Django 模板中static和 get_static_prefix标签的区别

把网站的静态文件从本地转到对象存储里后，发现了几个没有自动转向对象存储，还是指向原地址的链接。

检查发现正常使用的是用static标签写的，而那几个是用了get_static_prefix做拼接。

在Django文档中只是说要更自定义的方法就使用get_static_prefix并没有说明具体可能会有什么特征。那就只能直接看源码了。 static的部分源码：

class StaticNode(template.Node):
    child_nodelists = ()

    def __init__(self, varname=None, path=None):
        if path is None:
            raise template.TemplateSyntaxError(
                "Static template nodes must be given a path to return.")
        self.path = path
        self.varname = varname

    def __repr__(self):
        return (
            f'{self.__class__.__name__}(varname={self.varname!r}, path={self.path!r})'
        )

    def url(self, context):
        path = self.path.resolve(context)
        return self.handle_simple(path)

    def render(self, context):
        url = self.url(context)
        if context.autoescape:
            url = conditional_escape(url)
        if self.varname is None:
            return url
        context[self.varname] = url
        return ''

    @classmethod
    def handle_simple(cls, path):
        if apps.is_installed('django.contrib.staticfiles'):
            from django.contrib.staticfiles.storage import staticfiles_storage
            return staticfiles_storage.url(path)
        else:
            return urljoin(PrefixNode.handle_simple("STATIC_URL"), quote(path))

    @classmethod
    def handle_token(cls, parser, token):
        """
        Class method to parse prefix node and return a Node.
        """
        bits = token.split_contents()

        if len(bits) < 2:
            raise template.TemplateSyntaxError(
                "'%s' takes at least one argument (path to file)" % bits[0])

        path = parser.compile_filter(bits[1])

        if len(bits) >= 2 and bits[-2] == 'as':
            varname = bits[3]
        else:
            varname = None

        return cls(varname, path)

可以看到static标签中handle_simple()方法内有个判断是否使用了staticfiles_storage的逻辑，使用了staticfiles_storage则会返回staticfiles_storage的url()方法，这就是static标签能正确返回对象存储中链接的原因。

而get_static_prefix标签如下，是直接去设定里去找STATIC_URL的。所以使用get_static_prefix要把STATIC_URL改为对象存储的url。

class PrefixNode(template.Node):

    def __repr__(self):
        return "<PrefixNode for %r>" % self.name

    def __init__(self, varname=None, name=None):
        if name is None:
            raise template.TemplateSyntaxError(
                "Prefix nodes must be given a name to return.")
        self.varname = varname
        self.name = name

    @classmethod
    def handle_token(cls, parser, token, name):
        """
        Class method to parse prefix node and return a Node.
        """
        # token.split_contents() isn't useful here because tags using this method don't accept variable as arguments
        tokens = token.contents.split()
        if len(tokens) > 1 and tokens[1] != 'as':
            raise template.TemplateSyntaxError(
                "First argument in '%s' must be 'as'" % tokens[0])
        if len(tokens) > 1:
            varname = tokens[2]
        else:
            varname = None
        return cls(varname, name)

    @classmethod
    def handle_simple(cls, name):
        try:
            from django.conf import settings
        except ImportError:
            prefix = ''
        else:
            prefix = iri_to_uri(getattr(settings, name, ''))
        return prefix

@register.tag
def get_static_prefix(parser, token):
    """
    Populate a template variable with the static prefix,
    ``settings.STATIC_URL``.

    Usage::

        {% get_static_prefix [as varname] %}

    Examples::

        {% get_static_prefix %}
        {% get_static_prefix as static_prefix %}
    """
    return PrefixNode.handle_token(parser, token, "STATIC_URL")