在Django中自定义filter并在template中的使用详解

Django内置的filter有很多，然而我们由于业务逻辑的特殊要求，有时候仍然会不够用，这个时候就需要我们自定义filter来实现相应的内容。接下来让我们从自定义一个get_range(value)来产生列表的filter开始吧。

首先在你的django app的models.py的同级目录建立一个templatetags的文件夹，并在里面新建一个init.py的空文件，这个文件确保了这个文件夹被当做一个python的包。在添加了templatetags模块之后，我们需要重新启动服务器才能使其有效。

polls/
  __init__.py
  models.py
  templatetags/
    __init__.py
  views.py

然后在templatetags中新建一个python文件，文件名就是以后需要加载到页面的自定义库的名字。在这里我们新建一个generalfilters.py文件。

polls/
  __init__.py
  models.py
  templatetags/
    __init__.py
    generalfilters.py
  views.py

为了让库生效，必须在文件里添加一个模块级别的register变量。它是template.Library的实例，确保了标签和过滤器的有效性。

编辑generalfilters.py，添加

from django import template
register=template.Library()
@register.filter
def get_range(value):
  return range(value)

上述代码中定义了一个生成列表的函数，@register.filter表示这个函数是一个过滤器。至此我们的生成列表的过滤器就已经写好了。接下来我们需要把这个过滤器的库加载到模板里。

在你想要使用的模板的顶部加上{% load generalfilters %}，就可以使用这个过滤器了。

{% for i in 5|get_range_bet_within %}
  {{i}}
{% endfor %}

运行结果

补充知识：Django 自定义筛选器：重写DateFieldListFilter

我就废话不多说了，大家还是直接看代码吧！

class MyDateTimeFilter(admin.filters.DateFieldListFilter):
  def __init__(self, *args, **kwargs):
    super(MyDateTimeFilter, self).__init__(*args, **kwargs)
 
    now = timezone.now()
    # When time zone support is enabled, convert "now" to the user's time
    # zone so Django's definition of "Today" matches what the user expects.
    if timezone.is_aware(now):
      now = timezone.localtime(now)
 
    filter_end_date = now.replace(hour=0, minute=0, second=0, microsecond=0)
 
    filter_start_date_for_one_week = filter_end_date - datetime.timedelta(days=7)
 
    month_with_day31 = [1,3,5,7,8,10,12]
    if filter_end_date.month in month_with_day31 and filter_end_date.day == 31 and filter_end_date.month != 3:
      if filter_end_date.month == 1:
        filter_start_date_for_one_month = filter_end_date.replace(year=filter_end_date.year-1, month=12)
      else:
        filter_start_date_for_one_month = filter_end_date.replace(month=filter_end_date.month-1, day=30)
    elif filter_end_date.month == 3 and filter_end_date.day in [29, 30, 31]:
      if is_leap_year(filter_end_date.year):
        filter_start_date_for_one_month = filter_end_date.replace(month=filter_end_date.month-1, day=29)
      else:
        filter_start_date_for_one_month = filter_end_date.replace(month=filter_end_date.month-1, day=28)
    else:
      if filter_end_date.month == 1:
        filter_start_date_for_one_month = filter_end_date.replace(year=filter_end_date.year-1, month=12)
      else:
        filter_start_date_for_one_month = filter_end_date.replace(month=filter_end_date.month-1)
    
    filter_start_date_for_six_month = ''
    filter_start_date_for_six_month_month = (filter_end_date.month - 6 + 12) % 12
    if filter_start_date_for_six_month_month == 0:
      filter_start_date_for_six_month_month = 12
    if filter_start_date_for_six_month_month in month_with_day31:
      if filter_end_date.month > 6:
        filter_start_date_for_six_month = filter_end_date.replace(month=filter_start_date_for_six_month_month)
      else:
        filter_start_date_for_six_month = filter_end_date.replace(year=filter_end_date.year-1, month=filter_start_date_for_six_month_month)
    elif filter_start_date_for_six_month_month == 2:
      if filter_end_date.day in [29, 30, 31]:
        if is_leap_year(filter_end_date.year):
          filter_start_date_for_six_month = filter_end_date.replace(month=filter_start_date_for_six_month_month, day=29)
        else:
          filter_start_date_for_six_month = filter_end_date.replace(month=filter_start_date_for_six_month_month, day=28)
      else:
        filter_start_date_for_six_month = filter_end_date.replace(month=filter_start_date_for_six_month_month)
    else:
      if filter_end_date.day == 31 and filter_end_date.month >6:
        filter_start_date_for_six_month = filter_end_date.replace(month=filter_start_date_for_six_month_month, day=30)
      elif filter_end_date.day == 31 and filter_end_date.month <=6:
        filter_start_date_for_six_month = filter_end_date.replace(year=filter_end_date.year-1, month=filter_start_date_for_six_month_month, day=30)
      elif filter_end_date.day <31 and filter_end_date.month >6:
        filter_start_date_for_six_month = filter_end_date.replace(month=filter_start_date_for_six_month_month)
      else:
        filter_start_date_for_six_month = filter_end_date.replace(year=filter_end_date.year-1, month=filter_start_date_for_six_month_month)
 
    filter_end_date = filter_end_date + datetime.timedelta(days=1)
 
    self.links = ((
      ('------', {}),
      ('Past week', {
        self.lookup_kwarg_since: str(filter_start_date_for_one_week),
        self.lookup_kwarg_until: str(filter_end_date),
      }),
      ('Past month', {
        self.lookup_kwarg_since: str(filter_start_date_for_one_month),
        self.lookup_kwarg_until: str(filter_end_date),
      }),
      ('Past 6 months', {
        self.lookup_kwarg_since: str(filter_start_date_for_six_month),
        self.lookup_kwarg_until: str(filter_end_date),
      }),
      ('All', {}),
    ))

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