懂得 PHP 依赖注入 | Laravel IoC容器-php教程-PHP中文網

首頁

後端開發

php教程

懂得 PHP 依赖注入 | Laravel IoC容器

WBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWB

Jun 13, 2016 pm 12:28 PM

connectionfunctiongtnew

理解 PHP 依赖注入 | Laravel IoC容器

　　Laravel框架的依赖注入确实很强大，并且通过容器实现依赖注入可以有选择性的加载需要的服务，减少初始化框架的开销，下面是我在网上看到的一个帖子，写的很好拿来与大家分享，文章从开始按照传统的类设计数据库连接一直到通过容器加载服务这个高度解耦的设计展示了依赖注入的强大之处，值得我们借鉴和学习。

-----------------------------------------------------------分割线下面是大牛的原文----------------------------------------------------------

原文连接（http://www.yuansir-web.com/2014/03/20）

　　首先，我们假设，我们要开发一个组件命名为SomeComponent。这个组件中现在将要注入一个数据库连接。在这个例子中，数据库连接在component中被创建，这种方法是不切实际的，这样做的话，我们将不能改变数据库连接参数及数据库类型等一些参数。

<span style="color: #008080;"> 1</span> <span style="color: #000000;">php</span><span style="color: #008080;"> 2</span> <span style="color: #008080;"> 3</span> <span style="color: #0000ff;">class</span><span style="color: #000000;"> SomeComponent</span><span style="color: #008080;"> 4</span> <span style="color: #000000;">{</span><span style="color: #008080;"> 5</span> <span style="color: #008080;"> 6</span>     <span style="color: #008000;">/*</span><span style="color: #008000;">*</span><span style="color: #008080;"> 7</span> <span style="color: #008000;">     * The instantiation of the connection is hardcoded inside</span><span style="color: #008080;"> 8</span> <span style="color: #008000;">     * the component so is difficult to replace it externally</span><span style="color: #008080;"> 9</span> <span style="color: #008000;">     * or change its behavior</span><span style="color: #008080;">10</span>      <span style="color: #008000;">*/</span><span style="color: #008080;">11</span>     <span style="color: #0000ff;">public</span> <span style="color: #0000ff;">function</span><span style="color: #000000;"> someDbTask()</span><span style="color: #008080;">12</span> <span style="color: #000000;">    {</span><span style="color: #008080;">13</span>         <span style="color: #800080;">$connection</span> = <span style="color: #0000ff;">new</span> Connection(<span style="color: #0000ff;">array</span><span style="color: #000000;">(</span><span style="color: #008080;">14</span>             "host" => "localhost",<span style="color: #008080;">15</span>             "username" => "root",<span style="color: #008080;">16</span>             "password" => "secret",<span style="color: #008080;">17</span>             "dbname" => "invo"<span style="color: #008080;">18</span> <span style="color: #000000;">        ));</span><span style="color: #008080;">19</span> <span style="color: #008080;">20</span>         <span style="color: #008000;">//</span><span style="color: #008000;"> ...</span><span style="color: #008080;">21</span> <span style="color: #000000;">    }</span><span style="color: #008080;">22</span> <span style="color: #008080;">23</span> <span style="color: #000000;">}</span><span style="color: #008080;">24</span> <span style="color: #008080;">25</span> <span style="color: #800080;">$some</span> = <span style="color: #0000ff;">new</span><span style="color: #000000;"> SomeComponent();</span><span style="color: #008080;">26</span> <span style="color: #800080;">$some</span>->someDbTask();

为了解决上面所说的问题，我们需要在使用前创建一个外部连接，并注入到容器中。就目前而言，这看起来是一个很好的解决方案：

<span style="color: #008080;"> 1</span> <span style="color: #000000;">php</span><span style="color: #008080;"> 2</span> <span style="color: #008080;"> 3</span> <span style="color: #0000ff;">class</span><span style="color: #000000;"> SomeComponent</span><span style="color: #008080;"> 4</span> <span style="color: #000000;">{</span><span style="color: #008080;"> 5</span> <span style="color: #008080;"> 6</span>     <span style="color: #0000ff;">protected</span> <span style="color: #800080;">$_connection</span><span style="color: #000000;">;</span><span style="color: #008080;"> 7</span> <span style="color: #008080;"> 8</span>     <span style="color: #008000;">/*</span><span style="color: #008000;">*</span><span style="color: #008080;"> 9</span> <span style="color: #008000;">     * Sets the connection externally</span><span style="color: #008080;">10</span>      <span style="color: #008000;">*/</span><span style="color: #008080;">11</span>     <span style="color: #0000ff;">public</span> <span style="color: #0000ff;">function</span> setConnection(<span style="color: #800080;">$connection</span><span style="color: #000000;">)</span><span style="color: #008080;">12</span> <span style="color: #000000;">    {</span><span style="color: #008080;">13</span>         <span style="color: #800080;">$this</span>->_connection = <span style="color: #800080;">$connection</span><span style="color: #000000;">;</span><span style="color: #008080;">14</span> <span style="color: #000000;">    }</span><span style="color: #008080;">15</span> <span style="color: #008080;">16</span>     <span style="color: #0000ff;">public</span> <span style="color: #0000ff;">function</span><span style="color: #000000;"> someDbTask()</span><span style="color: #008080;">17</span> <span style="color: #000000;">    {</span><span style="color: #008080;">18</span>         <span style="color: #800080;">$connection</span> = <span style="color: #800080;">$this</span>-><span style="color: #000000;">_connection;</span><span style="color: #008080;">19</span> <span style="color: #008080;">20</span>         <span style="color: #008000;">//</span><span style="color: #008000;"> ...</span><span style="color: #008080;">21</span> <span style="color: #000000;">    }</span><span style="color: #008080;">22</span> <span style="color: #008080;">23</span> <span style="color: #000000;">}</span><span style="color: #008080;">24</span> <span style="color: #008080;">25</span> <span style="color: #800080;">$some</span> = <span style="color: #0000ff;">new</span><span style="color: #000000;"> SomeComponent();</span><span style="color: #008080;">26</span> <span style="color: #008080;">27</span> <span style="color: #008000;">//</span><span style="color: #008000;">Create the connection</span><span style="color: #008080;">28</span> <span style="color: #800080;">$connection</span> = <span style="color: #0000ff;">new</span> Connection(<span style="color: #0000ff;">array</span><span style="color: #000000;">(</span><span style="color: #008080;">29</span>     "host" => "localhost",<span style="color: #008080;">30</span>     "username" => "root",<span style="color: #008080;">31</span>     "password" => "secret",<span style="color: #008080;">32</span>     "dbname" => "invo"<span style="color: #008080;">33</span> <span style="color: #000000;">));</span><span style="color: #008080;">34</span> <span style="color: #008080;">35</span> <span style="color: #008000;">//</span><span style="color: #008000;">Inject the connection in the component</span><span style="color: #008080;">36</span> <span style="color: #800080;">$some</span>->setConnection(<span style="color: #800080;">$connection</span><span style="color: #000000;">);</span><span style="color: #008080;">37</span> <span style="color: #008080;">38</span> <span style="color: #800080;">$some</span>->someDbTask();

　　现在我们来考虑一个问题，我们在应用程序中的不同地方使用此组件，将多次创建数据库连接。使用一种类似全局注册表的方式，从这获得一个数据库连接实例，而不是使用一次就创建一次。

<span style="color: #008080;"> 1</span> <span style="color: #000000;">php</span><span style="color: #008080;"> 2</span> <span style="color: #008080;"> 3</span> <span style="color: #0000ff;">class</span><span style="color: #000000;"> Registry</span><span style="color: #008080;"> 4</span> <span style="color: #000000;">{</span><span style="color: #008080;"> 5</span> <span style="color: #008080;"> 6</span>     <span style="color: #008000;">/*</span><span style="color: #008000;">*</span><span style="color: #008080;"> 7</span> <span style="color: #008000;">     * Returns the connection</span><span style="color: #008080;"> 8</span>      <span style="color: #008000;">*/</span><span style="color: #008080;"> 9</span>     <span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">function</span><span style="color: #000000;"> getConnection()</span><span style="color: #008080;">10</span> <span style="color: #000000;">    {</span><span style="color: #008080;">11</span>        <span style="color: #0000ff;">return</span> <span style="color: #0000ff;">new</span> Connection(<span style="color: #0000ff;">array</span><span style="color: #000000;">(</span><span style="color: #008080;">12</span>             "host" => "localhost",<span style="color: #008080;">13</span>             "username" => "root",<span style="color: #008080;">14</span>             "password" => "secret",<span style="color: #008080;">15</span>             "dbname" => "invo"<span style="color: #008080;">16</span> <span style="color: #000000;">        ));</span><span style="color: #008080;">17</span> <span style="color: #000000;">    }</span><span style="color: #008080;">18</span> <span style="color: #008080;">19</span> <span style="color: #000000;">}</span><span style="color: #008080;">20</span> <span style="color: #008080;">21</span> <span style="color: #0000ff;">class</span><span style="color: #000000;"> SomeComponent</span><span style="color: #008080;">22</span> <span style="color: #000000;">{</span><span style="color: #008080;">23</span> <span style="color: #008080;">24</span>     <span style="color: #0000ff;">protected</span> <span style="color: #800080;">$_connection</span><span style="color: #000000;">;</span><span style="color: #008080;">25</span> <span style="color: #008080;">26</span>     <span style="color: #008000;">/*</span><span style="color: #008000;">*</span><span style="color: #008080;">27</span> <span style="color: #008000;">     * Sets the connection externally</span><span style="color: #008080;">28</span>      <span style="color: #008000;">*/</span><span style="color: #008080;">29</span>     <span style="color: #0000ff;">public</span> <span style="color: #0000ff;">function</span> setConnection(<span style="color: #800080;">$connection</span><span style="color: #000000;">){</span><span style="color: #008080;">30</span>         <span style="color: #800080;">$this</span>->_connection = <span style="color: #800080;">$connection</span><span style="color: #000000;">;</span><span style="color: #008080;">31</span> <span style="color: #000000;">    }</span><span style="color: #008080;">32</span> <span style="color: #008080;">33</span>     <span style="color: #0000ff;">public</span> <span style="color: #0000ff;">function</span><span style="color: #000000;"> someDbTask()</span><span style="color: #008080;">34</span> <span style="color: #000000;">    {</span><span style="color: #008080;">35</span>         <span style="color: #800080;">$connection</span> = <span style="color: #800080;">$this</span>-><span style="color: #000000;">_connection;</span><span style="color: #008080;">36</span> <span style="color: #008080;">37</span>         <span style="color: #008000;">//</span><span style="color: #008000;"> ...</span><span style="color: #008080;">38</span> <span style="color: #000000;">    }</span><span style="color: #008080;">39</span> <span style="color: #008080;">40</span> <span style="color: #000000;">}</span><span style="color: #008080;">41</span> <span style="color: #008080;">42</span> <span style="color: #800080;">$some</span> = <span style="color: #0000ff;">new</span><span style="color: #000000;"> SomeComponent();</span><span style="color: #008080;">43</span> <span style="color: #008080;">44</span> <span style="color: #008000;">//</span><span style="color: #008000;">Pass the connection defined in the registry</span><span style="color: #008080;">45</span> <span style="color: #800080;">$some</span>->setConnection(Registry::<span style="color: #000000;">getConnection());</span><span style="color: #008080;">46</span> <span style="color: #008080;">47</span> <span style="color: #800080;">$some</span>->someDbTask();

　　现在，让我们来想像一下，我们必须在组件中实现两个方法，首先需要创建一个新的数据库连接，第二个总是获得一个共享连接：

<span style="color: #008080;"> 1</span> <span style="color: #000000;">php</span><span style="color: #008080;"> 2</span> <span style="color: #008080;"> 3</span> <span style="color: #0000ff;">class</span><span style="color: #000000;"> Registry</span><span style="color: #008080;"> 4</span> <span style="color: #000000;">{</span><span style="color: #008080;"> 5</span> <span style="color: #008080;"> 6</span>     <span style="color: #0000ff;">protected</span> <span style="color: #0000ff;">static</span> <span style="color: #800080;">$_connection</span><span style="color: #000000;">;</span><span style="color: #008080;"> 7</span> <span style="color: #008080;"> 8</span>     <span style="color: #008000;">/*</span><span style="color: #008000;">*</span><span style="color: #008080;"> 9</span> <span style="color: #008000;">     * Creates a connection</span><span style="color: #008080;">10</span>      <span style="color: #008000;">*/</span><span style="color: #008080;">11</span>     <span style="color: #0000ff;">protected</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">function</span><span style="color: #000000;"> _createConnection()</span><span style="color: #008080;">12</span> <span style="color: #000000;">    {</span><span style="color: #008080;">13</span>         <span style="color: #0000ff;">return</span> <span style="color: #0000ff;">new</span> Connection(<span style="color: #0000ff;">array</span><span style="color: #000000;">(</span><span style="color: #008080;">14</span>             "host" => "localhost",<span style="color: #008080;">15</span>             "username" => "root",<span style="color: #008080;">16</span>             "password" => "secret",<span style="color: #008080;">17</span>             "dbname" => "invo"<span style="color: #008080;">18</span> <span style="color: #000000;">        ));</span><span style="color: #008080;">19</span> <span style="color: #000000;">    }</span><span style="color: #008080;">20</span> <span style="color: #008080;">21</span>     <span style="color: #008000;">/*</span><span style="color: #008000;">*</span><span style="color: #008080;">22</span> <span style="color: #008000;">     * Creates a connection only once and returns it</span><span style="color: #008080;">23</span>      <span style="color: #008000;">*/</span><span style="color: #008080;">24</span>     <span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">function</span><span style="color: #000000;"> getSharedConnection()</span><span style="color: #008080;">25</span> <span style="color: #000000;">    {</span><span style="color: #008080;">26</span>         <span style="color: #0000ff;">if</span> (self::<span style="color: #800080;">$_connection</span>===<span style="color: #0000ff;">null</span><span style="color: #000000;">){</span><span style="color: #008080;">27</span>             <span style="color: #800080;">$connection</span> = self::<span style="color: #000000;">_createConnection();</span><span style="color: #008080;">28</span>             self::<span style="color: #800080;">$_connection</span> = <span style="color: #800080;">$connection</span><span style="color: #000000;">;</span><span style="color: #008080;">29</span> <span style="color: #000000;">        }</span><span style="color: #008080;">30</span>         <span style="color: #0000ff;">return</span> self::<span style="color: #800080;">$_connection</span><span style="color: #000000;">;</span><span style="color: #008080;">31</span> <span style="color: #000000;">    }</span><span style="color: #008080;">32</span> <span style="color: #008080;">33</span>     <span style="color: #008000;">/*</span><span style="color: #008000;">*</span><span style="color: #008080;">34</span> <span style="color: #008000;">     * Always returns a new connection</span><span style="color: #008080;">35</span>      <span style="color: #008000;">*/</span><span style="color: #008080;">36</span>     <span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">function</span><span style="color: #000000;"> getNewConnection()</span><span style="color: #008080;">37</span> <span style="color: #000000;">    {</span><span style="color: #008080;">38</span>         <span style="color: #0000ff;">return</span> self::<span style="color: #000000;">_createConnection();</span><span style="color: #008080;">39</span> <span style="color: #000000;">    }</span><span style="color: #008080;">40</span> <span style="color: #008080;">41</span> <span style="color: #000000;">}</span><span style="color: #008080;">42</span> <span style="color: #008080;">43</span> <span style="color: #0000ff;">class</span><span style="color: #000000;"> SomeComponent</span><span style="color: #008080;">44</span> <span style="color: #000000;">{</span><span style="color: #008080;">45</span> <span style="color: #008080;">46</span>     <span style="color: #0000ff;">protected</span> <span style="color: #800080;">$_connection</span><span style="color: #000000;">;</span><span style="color: #008080;">47</span> <span style="color: #008080;">48</span>     <span style="color: #008000;">/*</span><span style="color: #008000;">*</span><span style="color: #008080;">49</span> <span style="color: #008000;">     * Sets the connection externally</span><span style="color: #008080;">50</span>      <span style="color: #008000;">*/</span><span style="color: #008080;">51</span>     <span style="color: #0000ff;">public</span> <span style="color: #0000ff;">function</span> setConnection(<span style="color: #800080;">$connection</span><span style="color: #000000;">){</span><span style="color: #008080;">52</span>         <span style="color: #800080;">$this</span>->_connection = <span style="color: #800080;">$connection</span><span style="color: #000000;">;</span><span style="color: #008080;">53</span> <span style="color: #000000;">    }</span><span style="color: #008080;">54</span> <span style="color: #008080;">55</span>     <span style="color: #008000;">/*</span><span style="color: #008000;">*</span><span style="color: #008080;">56</span> <span style="color: #008000;">     * This method always needs the shared connection</span><span style="color: #008080;">57</span>      <span style="color: #008000;">*/</span><span style="color: #008080;">58</span>     <span style="color: #0000ff;">public</span> <span style="color: #0000ff;">function</span><span style="color: #000000;"> someDbTask()</span><span style="color: #008080;">59</span> <span style="color: #000000;">    {</span><span style="color: #008080;">60</span>         <span style="color: #800080;">$connection</span> = <span style="color: #800080;">$this</span>-><span style="color: #000000;">_connection;</span><span style="color: #008080;">61</span> <span style="color: #008080;">62</span>         <span style="color: #008000;">//</span><span style="color: #008000;"> ...</span><span style="color: #008080;">63</span> <span style="color: #000000;">    }</span><span style="color: #008080;">64</span> <span style="color: #008080;">65</span>     <span style="color: #008000;">/*</span><span style="color: #008000;">*</span><span style="color: #008080;">66</span> <span style="color: #008000;">     * This method always needs a new connection</span><span style="color: #008080;">67</span>      <span style="color: #008000;">*/</span><span style="color: #008080;">68</span>     <span style="color: #0000ff;">public</span> <span style="color: #0000ff;">function</span> someOtherDbTask(<span style="color: #800080;">$connection</span><span style="color: #000000;">)</span><span style="color: #008080;">69</span> <span style="color: #000000;">    {</span><span style="color: #008080;">70</span> <span style="color: #008080;">71</span> <span style="color: #000000;">    }</span><span style="color: #008080;">72</span> <span style="color: #008080;">73</span> <span style="color: #000000;">}</span><span style="color: #008080;">74</span> <span style="color: #008080;">75</span> <span style="color: #800080;">$some</span> = <span style="color: #0000ff;">new</span><span style="color: #000000;"> SomeComponent();</span><span style="color: #008080;">76</span> <span style="color: #008080;">77</span> <span style="color: #008000;">//</span><span style="color: #008000;">This injects the shared connection</span><span style="color: #008080;">78</span> <span style="color: #800080;">$some</span>->setConnection(Registry::<span style="color: #000000;">getSharedConnection());</span><span style="color: #008080;">79</span> <span style="color: #008080;">80</span> <span style="color: #800080;">$some</span>-><span style="color: #000000;">someDbTask();</span><span style="color: #008080;">81</span> <span style="color: #008080;">82</span> <span style="color: #008000;">//</span><span style="color: #008000;">Here, we always pass a new connection as parameter</span><span style="color: #008080;">83</span> <span style="color: #800080;">$some</span>->someOtherDbTask(Registry::getConnection());

　　到此为止，我们已经看到了如何使用依赖注入解决我们的问题。不是在代码内部创建依赖关系，而是让其作为一个参数传递，这使得我们的程序更容易维护，降低程序代码的耦合度，实现一种松耦合。但是从长远来看，这种形式的依赖注入也有一些缺点。

　　例如，如果组件中有较多的依赖关系，我们需要创建多个setter方法传递，或创建构造函数进行传递。另外，每次使用组件时，都需要创建依赖组件，使代码维护不太易，我们编写的代码可能像这样：

<span style="color: #008080;"> 1</span> <span style="color: #000000;">php</span><span style="color: #008080;"> 2</span> <span style="color: #008080;"> 3</span> <span style="color: #008000;">//</span><span style="color: #008000;">Create the dependencies or retrieve them from the registry</span><span style="color: #008080;"> 4</span> <span style="color: #800080;">$connection</span> = <span style="color: #0000ff;">new</span><span style="color: #000000;"> Connection();</span><span style="color: #008080;"> 5</span> <span style="color: #800080;">$session</span> = <span style="color: #0000ff;">new</span><span style="color: #000000;"> Session();</span><span style="color: #008080;"> 6</span> <span style="color: #800080;">$fileSystem</span> = <span style="color: #0000ff;">new</span><span style="color: #000000;"> FileSystem();</span><span style="color: #008080;"> 7</span> <span style="color: #800080;">$filter</span> = <span style="color: #0000ff;">new</span><span style="color: #000000;"> Filter();</span><span style="color: #008080;"> 8</span> <span style="color: #800080;">$selector</span> = <span style="color: #0000ff;">new</span><span style="color: #000000;"> Selector();</span><span style="color: #008080;"> 9</span> <span style="color: #008080;">10</span> <span style="color: #008000;">//</span><span style="color: #008000;">Pass them as constructor parameters</span><span style="color: #008080;">11</span> <span style="color: #800080;">$some</span> = <span style="color: #0000ff;">new</span> SomeComponent(<span style="color: #800080;">$connection</span>, <span style="color: #800080;">$session</span>, <span style="color: #800080;">$fileSystem</span>, <span style="color: #800080;">$filter</span>, <span style="color: #800080;">$selector</span><span style="color: #000000;">);</span><span style="color: #008080;">12</span> <span style="color: #008080;">13</span> <span style="color: #008000;">//</span><span style="color: #008000;"> ... or using setters</span><span style="color: #008080;">14</span> <span style="color: #008080;">15</span> <span style="color: #800080;">$some</span>->setConnection(<span style="color: #800080;">$connection</span><span style="color: #000000;">);</span><span style="color: #008080;">16</span> <span style="color: #800080;">$some</span>->setSession(<span style="color: #800080;">$session</span><span style="color: #000000;">);</span><span style="color: #008080;">17</span> <span style="color: #800080;">$some</span>->setFileSystem(<span style="color: #800080;">$fileSystem</span><span style="color: #000000;">);</span><span style="color: #008080;">18</span> <span style="color: #800080;">$some</span>->setFilter(<span style="color: #800080;">$filter</span><span style="color: #000000;">);</span><span style="color: #008080;">19</span> <span style="color: #800080;">$some</span>->setSelector(<span style="color: #800080;">$selector</span>);

　　我想，我们不得不在应用程序的许多地方创建这个对象。如果你不需要依赖的组件后，我们又要去代码注入部分移除构造函数中的参数或者是setter方法。为了解决这个问题，我们再次返回去使用一个全局注册表来创建组件。但是，在创建对象之前，它增加了一个新的抽象层：

<span style="color: #008080;"> 1</span> <span style="color: #000000;">php</span><span style="color: #008080;"> 2</span> <span style="color: #008080;"> 3</span> <span style="color: #0000ff;">class</span><span style="color: #000000;"> SomeComponent</span><span style="color: #008080;"> 4</span> <span style="color: #000000;">{</span><span style="color: #008080;"> 5</span> <span style="color: #008080;"> 6</span>     <span style="color: #008000;">//</span><span style="color: #008000;"> ...</span><span style="color: #008080;"> 7</span> <span style="color: #008080;"> 8</span>     <span style="color: #008000;">/*</span><span style="color: #008000;">*</span><span style="color: #008080;"> 9</span> <span style="color: #008000;">     * Define a factory method to create SomeComponent instances injecting its dependencies</span><span style="color: #008080;">10</span>      <span style="color: #008000;">*/</span><span style="color: #008080;">11</span>     <span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">function</span><span style="color: #000000;"> factory()</span><span style="color: #008080;">12</span> <span style="color: #000000;">    {</span><span style="color: #008080;">13</span> <span style="color: #008080;">14</span>         <span style="color: #800080;">$connection</span> = <span style="color: #0000ff;">new</span><span style="color: #000000;"> Connection();</span><span style="color: #008080;">15</span>         <span style="color: #800080;">$session</span> = <span style="color: #0000ff;">new</span><span style="color: #000000;"> Session();</span><span style="color: #008080;">16</span>         <span style="color: #800080;">$fileSystem</span> = <span style="color: #0000ff;">new</span><span style="color: #000000;"> FileSystem();</span><span style="color: #008080;">17</span>         <span style="color: #800080;">$filter</span> = <span style="color: #0000ff;">new</span><span style="color: #000000;"> Filter();</span><span style="color: #008080;">18</span>         <span style="color: #800080;">$selector</span> = <span style="color: #0000ff;">new</span><span style="color: #000000;"> Selector();</span><span style="color: #008080;">19</span> <span style="color: #008080;">20</span>         <span style="color: #0000ff;">return</span> <span style="color: #0000ff;">new</span> self(<span style="color: #800080;">$connection</span>, <span style="color: #800080;">$session</span>, <span style="color: #800080;">$fileSystem</span>, <span style="color: #800080;">$filter</span>, <span style="color: #800080;">$selector</span><span style="color: #000000;">);</span><span style="color: #008080;">21</span> <span style="color: #000000;">    }</span><span style="color: #008080;">22</span> <span style="color: #008080;">23</span> }

　　这一刻，我们好像回到了问题的开始，我们正在创建组件内部的依赖，我们每次都在修改以及找寻一种解决问题的办法，但这都不是很好的做法。

　　一种实用和优雅的来解决这些问题，是使用容器的依赖注入，像我们在前面看到的，容器作为全局注册表，使用容器的依赖注入做为一种桥梁来解决依赖可以使我们的代码耦合度更低，很好的降低了组件的复杂性：

<span style="color: #008080;"> 1</span> <span style="color: #000000;">php</span><span style="color: #008080;"> 2</span> <span style="color: #008080;"> 3</span> <span style="color: #0000ff;">class</span><span style="color: #000000;"> SomeComponent</span><span style="color: #008080;"> 4</span> <span style="color: #000000;">{</span><span style="color: #008080;"> 5</span> <span style="color: #008080;"> 6</span>     <span style="color: #0000ff;">protected</span> <span style="color: #800080;">$_di</span><span style="color: #000000;">;</span><span style="color: #008080;"> 7</span> <span style="color: #008080;"> 8</span>     <span style="color: #0000ff;">public</span> <span style="color: #0000ff;">function</span> __construct(<span style="color: #800080;">$di</span><span style="color: #000000;">)</span><span style="color: #008080;"> 9</span> <span style="color: #000000;">    {</span><span style="color: #008080;">10</span>         <span style="color: #800080;">$this</span>->_di = <span style="color: #800080;">$di</span><span style="color: #000000;">;</span><span style="color: #008080;">11</span> <span style="color: #000000;">    }</span><span style="color: #008080;">12</span> <span style="color: #008080;">13</span>     <span style="color: #0000ff;">public</span> <span style="color: #0000ff;">function</span><span style="color: #000000;"> someDbTask()</span><span style="color: #008080;">14</span> <span style="color: #000000;">    {</span><span style="color: #008080;">15</span> <span style="color: #008080;">16</span>         <span style="color: #008000;">//</span><span style="color: #008000;"> Get the connection service</span><span style="color: #008080;">17</span> <span style="color: #008000;">        // Always returns a new connection</span><span style="color: #008080;">18</span>         <span style="color: #800080;">$connection</span> = <span style="color: #800080;">$this</span>->_di->get('db'<span style="color: #000000;">);</span><span style="color: #008080;">19</span> <span style="color: #008080;">20</span> <span style="color: #000000;">    }</span><span style="color: #008080;">21</span> <span style="color: #008080;">22</span>     <span style="color: #0000ff;">public</span> <span style="color: #0000ff;">function</span><span style="color: #000000;"> someOtherDbTask()</span><span style="color: #008080;">23</span> <span style="color: #000000;">    {</span><span style="color: #008080;">24</span> <span style="color: #008080;">25</span>         <span style="color: #008000;">//</span><span style="color: #008000;"> Get a shared connection service,</span><span style="color: #008080;">26</span> <span style="color: #008000;">        // this will return the same connection everytime</span><span style="color: #008080;">27</span>         <span style="color: #800080;">$connection</span> = <span style="color: #800080;">$this</span>->_di->getShared('db'<span style="color: #000000;">);</span><span style="color: #008080;">28</span> <span style="color: #008080;">29</span>         <span style="color: #008000;">//</span><span style="color: #008000;">This method also requires a input filtering service</span><span style="color: #008080;">30</span>         <span style="color: #800080;">$filter</span> = <span style="color: #800080;">$this</span>->_db->get('filter'<span style="color: #000000;">);</span><span style="color: #008080;">31</span> <span style="color: #008080;">32</span> <span style="color: #000000;">    }</span><span style="color: #008080;">33</span> <span style="color: #008080;">34</span> <span style="color: #000000;">}</span><span style="color: #008080;">35</span> <span style="color: #008080;">36</span> <span style="color: #800080;">$di</span> = <span style="color: #0000ff;">new</span><span style="color: #000000;"> Phalcon\DI();</span><span style="color: #008080;">37</span> <span style="color: #008080;">38</span> <span style="color: #008000;">//</span><span style="color: #008000;">Register a "db" service in the container</span><span style="color: #008080;">39</span> <span style="color: #800080;">$di</span>->set('db', <span style="color: #0000ff;">function</span><span style="color: #000000;">(){</span><span style="color: #008080;">40</span>     <span style="color: #0000ff;">return</span> <span style="color: #0000ff;">new</span> Connection(<span style="color: #0000ff;">array</span><span style="color: #000000;">(</span><span style="color: #008080;">41</span>         "host" => "localhost",<span style="color: #008080;">42</span>         "username" => "root",<span style="color: #008080;">43</span>         "password" => "secret",<span style="color: #008080;">44</span>         "dbname" => "invo"<span style="color: #008080;">45</span> <span style="color: #000000;">    ));</span><span style="color: #008080;">46</span> <span style="color: #000000;">});</span><span style="color: #008080;">47</span> <span style="color: #008080;">48</span> <span style="color: #008000;">//</span><span style="color: #008000;">Register a "filter" service in the container</span><span style="color: #008080;">49</span> <span style="color: #800080;">$di</span>->set('filter', <span style="color: #0000ff;">function</span><span style="color: #000000;">(){</span><span style="color: #008080;">50</span>     <span style="color: #0000ff;">return</span> <span style="color: #0000ff;">new</span><span style="color: #000000;"> Filter();</span><span style="color: #008080;">51</span> <span style="color: #000000;">});</span><span style="color: #008080;">52</span> <span style="color: #008080;">53</span> <span style="color: #008000;">//</span><span style="color: #008000;">Register a "session" service in the container</span><span style="color: #008080;">54</span> <span style="color: #800080;">$di</span>->set('session', <span style="color: #0000ff;">function</span><span style="color: #000000;">(){</span><span style="color: #008080;">55</span>     <span style="color: #0000ff;">return</span> <span style="color: #0000ff;">new</span><span style="color: #000000;"> Session();</span><span style="color: #008080;">56</span> <span style="color: #000000;">});</span><span style="color: #008080;">57</span> <span style="color: #008080;">58</span> <span style="color: #008000;">//</span><span style="color: #008000;">Pass the service container as unique parameter</span><span style="color: #008080;">59</span> <span style="color: #800080;">$some</span> = <span style="color: #0000ff;">new</span> SomeComponent(<span style="color: #800080;">$di</span><span style="color: #000000;">);</span><span style="color: #008080;">60</span> <span style="color: #008080;">61</span> <span style="color: #800080;">$some</span>->someTask();

现在，该组件只有访问某种service的时候才需要它，如果它不需要，它甚至不初始化，以节约资源。该组件是高度解耦。他们的行为，或者说他们的任何其他方面都不会影响到组件本身。
我们的实现办法¶

Phalcon\DI 是一个实现了服务的依赖注入功能的组件，它本身也是一个容器。

由于Phalcon高度解耦，Phalcon\DI 是框架用来集成其他组件的必不可少的部分，开发人员也可以使用这个组件依赖注入和管理应用程序中不同类文件的实例。

基本上，这个组件实现了 Inversion of Control 模式。基于此，对象不再以构造函数接收参数或者使用setter的方式来实现注入，而是直接请求服务的依赖注入。这就大大降低了整体程序的复杂性，因为只有一个方法用以获得所需要的一个组件的依赖关系。

此外，这种模式增强了代码的可测试性，从而使它不容易出错。
在容器中注册服务¶

框架本身或开发人员都可以注册服务。当一个组件A要求调用组件B（或它的类的一个实例），可以从容器中请求调用组件B，而不是创建组件B的一个实例。

这种工作方式为我们提供了许多优点：

我们可以更换一个组件，从他们本身或者第三方轻松创建。
在组件发布之前，我们可以充分的控制对象的初始化，并对对象进行各种设置。
我们可以使用统一的方式从组件得到一个结构化的全局实例

服务可以通过以下几种方式注入到容器：

<span style="color: #008080;"> 1</span> <span style="color: #000000;">php</span><span style="color: #008080;"> 2</span> <span style="color: #008080;"> 3</span> <span style="color: #008000;">//</span><span style="color: #008000;">Create the Dependency Injector Container</span><span style="color: #008080;"> 4</span> <span style="color: #800080;">$di</span> = <span style="color: #0000ff;">new</span><span style="color: #000000;"> Phalcon\DI();</span><span style="color: #008080;"> 5</span> <span style="color: #008080;"> 6</span> <span style="color: #008000;">//</span><span style="color: #008000;">By its class name</span><span style="color: #008080;"> 7</span> <span style="color: #800080;">$di</span>->set("request", 'Phalcon\Http\Request'<span style="color: #000000;">);</span><span style="color: #008080;"> 8</span> <span style="color: #008080;"> 9</span> <span style="color: #008000;">//</span><span style="color: #008000;">Using an anonymous function, the instance will lazy loaded</span><span style="color: #008080;">10</span> <span style="color: #800080;">$di</span>->set("request", <span style="color: #0000ff;">function</span><span style="color: #000000;">(){</span><span style="color: #008080;">11</span>     <span style="color: #0000ff;">return</span> <span style="color: #0000ff;">new</span><span style="color: #000000;"> Phalcon\Http\Request();</span><span style="color: #008080;">12</span> <span style="color: #000000;">});</span><span style="color: #008080;">13</span> <span style="color: #008080;">14</span> <span style="color: #008000;">//</span><span style="color: #008000;">Registering directly an instance</span><span style="color: #008080;">15</span> <span style="color: #800080;">$di</span>->set("request", <span style="color: #0000ff;">new</span><span style="color: #000000;"> Phalcon\Http\Request());</span><span style="color: #008080;">16</span> <span style="color: #008080;">17</span> <span style="color: #008000;">//</span><span style="color: #008000;">Using an array definition</span><span style="color: #008080;">18</span> <span style="color: #800080;">$di</span>->set("request", <span style="color: #0000ff;">array</span><span style="color: #000000;">(</span><span style="color: #008080;">19</span>     "className" => 'Phalcon\Http\Request'<span style="color: #008080;">20</span> ));

在上面的例子中，当向框架请求访问一个请求数据时，它将首先确定容器中是否存在这个”reqeust”名称的服务。

容器会反回一个请求数据的实例，开发人员最终得到他们想要的组件。

在上面示例中的每一种方法都有优缺点，具体使用哪一种，由开发过程中的特定场景来决定的。

用一个字符串来设定一个服务非常简单，但缺少灵活性。设置服务时，使用数组则提供了更多的灵活性，而且可以使用较复杂的代码。lambda函数是两者之间一个很好的平衡，但也可能导致更多的维护管理成本。

Phalcon\DI 提供服务的延迟加载。除非开发人员在注入服务的时候直接实例化一个对象，然后存存储到容器中。在容器中，通过数组，字符串等方式存储的服务都将被延迟加载，即只有在请求对象的时候才被初始化。

<span style="color: #008080;"> 1</span> <span style="color: #000000;">php</span><span style="color: #008080;"> 2</span> <span style="color: #008080;"> 3</span> <span style="color: #008000;">//</span><span style="color: #008000;">Register a service "db" with a class name and its parameters</span><span style="color: #008080;"> 4</span> <span style="color: #800080;">$di</span>->set("db", <span style="color: #0000ff;">array</span><span style="color: #000000;">(</span><span style="color: #008080;"> 5</span>     "className" => "Phalcon\Db\Adapter\Pdo\Mysql",<span style="color: #008080;"> 6</span>     "parameters" => <span style="color: #0000ff;">array</span><span style="color: #000000;">(</span><span style="color: #008080;"> 7</span>           "parameter" => <span style="color: #0000ff;">array</span><span style="color: #000000;">(</span><span style="color: #008080;"> 8</span>                "host" => "localhost",<span style="color: #008080;"> 9</span>                "username" => "root",<span style="color: #008080;">10</span>                "password" => "secret",<span style="color: #008080;">11</span>                "dbname" => "blog"<span style="color: #008080;">12</span> <span style="color: #000000;">          )</span><span style="color: #008080;">13</span> <span style="color: #000000;">    )</span><span style="color: #008080;">14</span> <span style="color: #000000;">));</span><span style="color: #008080;">15</span> <span style="color: #008080;">16</span> <span style="color: #008000;">//</span><span style="color: #008000;">Using an anonymous function</span><span style="color: #008080;">17</span> <span style="color: #800080;">$di</span>->set("db", <span style="color: #0000ff;">function</span><span style="color: #000000;">(){</span><span style="color: #008080;">18</span>     <span style="color: #0000ff;">return</span> <span style="color: #0000ff;">new</span> Phalcon\Db\Adapter\Pdo\<span style="color: #008080;">Mysql</span>(<span style="color: #0000ff;">array</span><span style="color: #000000;">(</span><span style="color: #008080;">19</span>          "host" => "localhost",<span style="color: #008080;">20</span>          "username" => "root",<span style="color: #008080;">21</span>          "password" => "secret",<span style="color: #008080;">22</span>          "dbname" => "blog"<span style="color: #008080;">23</span> <span style="color: #000000;">    ));</span><span style="color: #008080;">24</span> });

以上这两种服务的注册方式产生相同的结果。然后，通过数组定义的，在后面需要的时候，你可以修改服务参数：

<span style="color: #008080;">1</span> <span style="color: #000000;">php</span><span style="color: #008080;">2</span> <span style="color: #008080;">3</span> <span style="color: #800080;">$di</span>->setParameter("db", 0, <span style="color: #0000ff;">array</span><span style="color: #000000;">(</span><span style="color: #008080;">4</span>     "host" => "localhost",<span style="color: #008080;">5</span>     "username" => "root",<span style="color: #008080;">6</span>     "password" => "secret"<span style="color: #008080;">7</span> ));

从容器中获得服务的最简单方式就是使用”get”方法，它将从容器中返回一个新的实例：

<span style="color: #008080;">1</span> <span style="color: #000000;">php</span><span style="color: #008080;">2</span>      <span style="color: #800080;">$request</span> = <span style="color: #800080;">$di</span>->get("request");

或者通过下面这种魔术方法的形式调用：

<span style="color: #008080;">1</span> <span style="color: #000000;">php</span><span style="color: #008080;">2</span> <span style="color: #008080;">3</span> <span style="color: #800080;">$request</span> = <span style="color: #800080;">$di</span>-><span style="color: #000000;">getRequest();</span><span style="color: #008080;">4</span> <span style="color: #008080;">5</span> Phalcon\DI 同时允许服务重用，为了得到一个已经实例化过的服务，可以使用 getShared() 方法的形式来获得服务。

具体的 Phalcon\Http\Request 请求示例：

<span style="color: #008080;">1</span> <span style="color: #000000;">php</span><span style="color: #008080;">2</span> <span style="color: #008080;">3</span> <span style="color: #800080;">$request</span> = <span style="color: #800080;">$di</span>->getShared("request");

参数还可以在请求的时候通过将一个数组参数传递给构造函数的方式：

<span style="color: #008080;">1</span> <span style="color: #000000;">php</span><span style="color: #008080;">2</span> <span style="color: #008080;">3</span> <span style="color: #800080;">$component</span> = <span style="color: #800080;">$di</span>->get("MyComponent", <span style="color: #0000ff;">array</span>("some-parameter", "other"))

陳述

本文內容由網友自願投稿，版權歸原作者所有。本站不承擔相應的法律責任。如發現涉嫌抄襲或侵權的內容，請聯絡admin@php.cn

PHP類型提示如何起作用，包括標量類型，返回類型，聯合類型和無效類型？Apr 17, 2025 am 12:25 AM

PHP類型提示提升代碼質量和可讀性。 1)標量類型提示：自PHP7.0起，允許在函數參數中指定基本數據類型，如int、float等。 2)返回類型提示：確保函數返回值類型的一致性。 3)聯合類型提示：自PHP8.0起，允許在函數參數或返回值中指定多個類型。 4)可空類型提示：允許包含null值，處理可能返回空值的函數。

PHP如何處理對象克隆（克隆關鍵字）和__clone魔法方法？Apr 17, 2025 am 12:24 AM

PHP中使用clone關鍵字創建對象副本，並通過\_\_clone魔法方法定制克隆行為。 1.使用clone關鍵字進行淺拷貝，克隆對象的屬性但不克隆對象屬性內的對象。 2.通過\_\_clone方法可以深拷貝嵌套對象，避免淺拷貝問題。 3.注意避免克隆中的循環引用和性能問題，優化克隆操作以提高效率。

PHP與Python：用例和應用程序Apr 17, 2025 am 12:23 AM

PHP適用於Web開發和內容管理系統，Python適合數據科學、機器學習和自動化腳本。 1.PHP在構建快速、可擴展的網站和應用程序方面表現出色，常用於WordPress等CMS。 2.Python在數據科學和機器學習領域表現卓越，擁有豐富的庫如NumPy和TensorFlow。

描述不同的HTTP緩存標頭（例如，Cache-Control，ETAG，最後修飾）。Apr 17, 2025 am 12:22 AM

HTTP緩存頭的關鍵玩家包括Cache-Control、ETag和Last-Modified。 1.Cache-Control用於控制緩存策略，示例：Cache-Control:max-age=3600,public。 2.ETag通過唯一標識符驗證資源變化，示例：ETag:"686897696a7c876b7e"。 3.Last-Modified指示資源最後修改時間，示例：Last-Modified:Wed,21Oct201507:28:00GMT。

說明PHP中的安全密碼散列（例如，password_hash，password_verify）。為什麼不使用MD5或SHA1？Apr 17, 2025 am 12:06 AM

在PHP中，應使用password_hash和password_verify函數實現安全的密碼哈希處理，不應使用MD5或SHA1。1)password_hash生成包含鹽值的哈希，增強安全性。 2)password_verify驗證密碼，通過比較哈希值確保安全。 3)MD5和SHA1易受攻擊且缺乏鹽值，不適合現代密碼安全。

PHP：服務器端腳本語言的簡介Apr 16, 2025 am 12:18 AM

PHP是一種服務器端腳本語言，用於動態網頁開發和服務器端應用程序。 1.PHP是一種解釋型語言，無需編譯，適合快速開發。 2.PHP代碼嵌入HTML中，易於網頁開發。 3.PHP處理服務器端邏輯，生成HTML輸出，支持用戶交互和數據處理。 4.PHP可與數據庫交互，處理表單提交，執行服務器端任務。

PHP和網絡：探索其長期影響Apr 16, 2025 am 12:17 AM

PHP在過去幾十年中塑造了網絡，並將繼續在Web開發中扮演重要角色。 1)PHP起源於1994年，因其易用性和與MySQL的無縫集成成為開發者首選。 2)其核心功能包括生成動態內容和與數據庫的集成，使得網站能夠實時更新和個性化展示。 3)PHP的廣泛應用和生態系統推動了其長期影響，但也面臨版本更新和安全性挑戰。 4)近年來的性能改進，如PHP7的發布，使其能與現代語言競爭。 5)未來，PHP需應對容器化、微服務等新挑戰，但其靈活性和活躍社區使其具備適應能力。