在 Django 模板中执行 getattr() 样式查找 [英] Performing a getattr() style lookup in a django template

问题描述

当您事先不知道某个属性的名称时，Python 的 getattr() 方法很有用.

Python's getattr() method is useful when you don't know the name of a certain attribute in advance.

这个功能在模板中也会派上用场，但我从来没有想出办法来做到这一点.是否有可以执行动态属性查找的内置标签或非内置标签?

This functionality would also come in handy in templates, but I've never figured out a way to do it. Is there a built-in tag or non-built-in tag that can perform dynamic attribute lookups?

推荐答案

我最近也不得不将此代码编写为自定义模板标签.为了处理所有查找场景，它首先进行标准属性查找，然后尝试进行字典查找，然后尝试 getitem 查找(使列表起作用)，然后遵循标准未找到对象时的 Django 模板行为.

I also had to write this code as a custom template tag recently. To handle all look-up scenarios, it first does a standard attribute look-up, then tries to do a dictionary look-up, then tries a getitem lookup (for lists to work), then follows standard Django template behavior when an object is not found.

(2009-08-26 更新，现在也处理列表索引查找)

(updated 2009-08-26 to now handle list index lookups as well)

# app/templatetags/getattribute.py

import re
from django import template
from django.conf import settings

numeric_test = re.compile("^d+$")
register = template.Library()

def getattribute(value, arg):
    """Gets an attribute of an object dynamically from a string name"""

    if hasattr(value, str(arg)):
        return getattr(value, arg)
    elif hasattr(value, 'has_key') and value.has_key(arg):
        return value[arg]
    elif numeric_test.match(str(arg)) and len(value) > int(arg):
        return value[int(arg)]
    else:
        return settings.TEMPLATE_STRING_IF_INVALID

register.filter('getattribute', getattribute)

模板使用:

{% load getattribute %}
{{ object|getattribute:dynamic_string_var }}

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