[PHP] 看博客学习观察者模式 - 陶士涵

具体应用场景是，当subject的某个动作需要引发一系列不同对象的动作（比如你是一个班长要去通知班里的某些人），与其一个一个的手动调用触发的方法（私下里一个一个通知），不如维护一个列表（建一个群），这个列表存有你想要调用的对象方法（想要通知的人）；之后每次做的触发的时候只要轮询这个列表就好了（群发），而不用关心这个列表里有谁，只用关心想让谁加入让谁退出

PHP版：

<span style="color: #008000;">//</span><span style="color: #008000;">这个是主题</span>
<span style="color: #0000ff;">class</span><span style="color: #000000;"> Paper{
    </span><span style="color: #0000ff;">private</span> <span style="color: #800080;">$_observers</span>=<span style="color: #0000ff;">array</span><span style="color: #000000;">();
    </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">function</span> register(<span style="color: #800080;">$obj</span><span style="color: #000000;">){
        </span><span style="color: #800080;">$this</span>->_observers[]=<span style="color: #800080;">$obj</span><span style="color: #000000;">;
    }
    </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">function</span><span style="color: #000000;"> start(){
        </span><span style="color: #0000ff;">if</span>(!<span style="color: #0000ff;">empty</span>(<span style="color: #800080;">$this</span>-><span style="color: #000000;">_observers)){
            </span><span style="color: #0000ff;">foreach</span>(<span style="color: #800080;">$this</span>->_observers <span style="color: #0000ff;">as</span> <span style="color: #800080;">$observer</span><span style="color: #000000;">){
                </span><span style="color: #800080;">$observer</span>-><span style="color: #000000;">todo();
            }
        }
    }
}

</span><span style="color: #008000;">//</span><span style="color: #008000;">这个是观察者</span>
<span style="color: #0000ff;">class</span><span style="color: #000000;"> observer{
    </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">function</span><span style="color: #000000;"> todo(){
        </span><span style="color: #0000ff;">echo</span> "我在做..."<span style="color: #000000;">;
    }
}

</span><span style="color: #800080;">$paper</span>=<span style="color: #0000ff;">new</span><span style="color: #000000;"> Paper();
</span><span style="color: #800080;">$paper</span>->register(<span style="color: #0000ff;">new</span><span style="color: #000000;"> observer());
</span><span style="color: #800080;">$paper</span>->register(<span style="color: #0000ff;">new</span><span style="color: #000000;"> observer());

</span><span style="color: #800080;">$paper</span>->start();

javascript版：

<span style="color: #008000;">//</span><span style="color: #008000;">这是主题</span>
<span style="color: #0000ff;">function</span><span style="color: #000000;"> Paper(){
    </span><span style="color: #0000ff;">this</span>.observers=<span style="color: #000000;">[];
    </span><span style="color: #0000ff;">this</span>.register=<span style="color: #0000ff;">function</span><span style="color: #000000;">(obj){
        </span><span style="color: #0000ff;">this</span><span style="color: #000000;">.observers.push(obj);
    }
    </span><span style="color: #0000ff;">this</span>.start=<span style="color: #0000ff;">function</span><span style="color: #000000;">(){
        </span><span style="color: #0000ff;">for</span>(<span style="color: #0000ff;">var</span> i=0;ithis.observers.length;i++<span style="color: #000000;">){
            </span><span style="color: #0000ff;">this</span><span style="color: #000000;">.observers[i].todo();
        }
    }
}
</span><span style="color: #008000;">//</span><span style="color: #008000;">这是观察者</span>
<span style="color: #0000ff;">function</span><span style="color: #000000;"> Observer(){
    </span><span style="color: #0000ff;">this</span>.todo=<span style="color: #0000ff;">function</span><span style="color: #000000;">(){
        console.log(</span>"我在做..."<span style="color: #000000;">);
    }
}

</span><span style="color: #0000ff;">var</span> paper=<span style="color: #0000ff;">new</span><span style="color: #000000;"> Paper();
paper.register(</span><span style="color: #0000ff;">new</span><span style="color: #000000;"> Observer());
paper.register(</span><span style="color: #0000ff;">new</span><span style="color: #000000;"> Observer());
paper.start();</span>

java版：

<span style="color: #0000ff;">package</span><span style="color: #000000;"> com.tsh.mthread;

</span><span style="color: #0000ff;">import</span><span style="color: #000000;"> java.util.ArrayList;
</span><span style="color: #0000ff;">import</span><span style="color: #000000;"> java.util.List;

</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">class</span><span style="color: #000000;"> Home {

    </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> main(String[] args) {
        Paper paper</span>=<span style="color: #0000ff;">new</span><span style="color: #000000;"> Paper();
        paper.register(</span><span style="color: #0000ff;">new</span><span style="color: #000000;"> Observer());
        paper.register(</span><span style="color: #0000ff;">new</span><span style="color: #000000;"> Observer());
        paper.start();
    }
    </span><span style="color: #008000;">//</span><span style="color: #008000;">这是主题</span>
    <span style="color: #0000ff;">private</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">class</span><span style="color: #000000;"> Paper{
        </span><span style="color: #0000ff;">private</span> List<observer> observers=<span style="color: #0000ff;">new</span> ArrayList<observer><span style="color: #000000;">();
        </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> register(Observer observer){
            observers.add(observer);
        }
        </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> start(){
            </span><span style="color: #0000ff;">if</span>(observers.size()!=0<span style="color: #000000;">){
                </span><span style="color: #0000ff;">for</span><span style="color: #000000;">(Observer observer:observers){
                    observer.todo();
                }
            }
        }
    }
    </span><span style="color: #008000;">//</span><span style="color: #008000;">这是观察者</span>
    <span style="color: #0000ff;">private</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">class</span><span style="color: #000000;"> Observer{
        </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> todo(){
            System.out.println(</span>"我在做..."<span style="color: #000000;">);
        }
    }
}</span></observer></observer>