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Django框架下在视图中使用模版的方法

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Jun 10, 2016 pm 03:09 PM

djangostencilview

打开current_datetime 视图。以下是其内容：

from django.http import HttpResponse
import datetime

def current_datetime(request):
  now = datetime.datetime.now()
  html = "<html><body>It is now %s.</body></html>" % now
  return HttpResponse(html)

让我们用 Django 模板系统来修改该视图。第一步，你可能已经想到了要做下面这样的修改：

from django.template import Template, Context
from django.http import HttpResponse
import datetime

def current_datetime(request):
  now = datetime.datetime.now()
  t = Template("<html><body>It is now {{ current_date }}.</body></html>")
  html = t.render(Context({'current_date': now}))
  return HttpResponse(html)

没错，它确实使用了模板系统，但是并没有解决我们在本章开头所指出的问题。也就是说，模板仍然嵌入在Python代码里，并未真正的实现数据与表现的分离。让我们将模板置于一个单独的文件中，并且让视图加载该文件来解决此问题。

你可能首先考虑把模板保存在文件系统的某个位置并用 Python 内建的文件操作函数来读取文件内容。假设文件保存在 /home/djangouser/templates/mytemplate.html 中的话，代码就会像下面这样:

from django.template import Template, Context
from django.http import HttpResponse
import datetime

def current_datetime(request):
  now = datetime.datetime.now()
  # Simple way of using templates from the filesystem.
  # This is BAD because it doesn't account for missing files!
  fp = open('/home/djangouser/templates/mytemplate.html')
  t = Template(fp.read())
  fp.close()
  html = t.render(Context({'current_date': now}))
  return HttpResponse(html)

然而，基于以下几个原因，该方法还算不上简洁：

它没有对文件丢失的情况做出处理。如果文件 mytemplate.html 不存在或者不可读， open() 函数调用将会引发 IOError 异常。
这里对模板文件的位置进行了硬编码。如果你在每个视图函数都用该技术，就要不断复制这些模板的位置。更不用说还要带来大量的输入工作！
它包含了大量令人生厌的重复代码。与其在每次加载模板时都调用 open() 、 fp.read() 和 fp.close() ，还不如做出更佳选择。

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