TemplateResponse and SimpleTemplateResponsePStandard HttpResponse objects are static structures.
They are provided with a block of pre-rendered content at time of
construction, and while that content can be modified, it isn't in a form that
makes it easy to perform modifications.
However, it can sometimes be beneficial to allow decorators or middleware to modify a response after it has been constructed by the view. For example, you may want to change the template that is used, or put additional data into the context.
TemplateResponse provides a way to do just that. Unlike basic
HttpResponse objects, TemplateResponse objects retain
the details of the template and context that was provided by the view to
compute the response. The final output of the response is not computed until
it is needed, later in the response process.
SimpleTemplateResponse objectsPSimpleTemplateResponse.template_namePThe name of the template to be rendered. Accepts a backend-dependent
template object (such as those returned by
get_template()), the name of a template,
or a list of template names.
Example: ['foo.html', 'path/to/bar.html']
SimpleTemplateResponse.context_dataPThe context data to be used when rendering the template. It must be a
dict.
Example: {'foo': 123}
SimpleTemplateResponse.rendered_contentPThe current rendered value of the response content, using the current template and context data.
SimpleTemplateResponse.is_renderedPA boolean indicating whether the response content has been rendered.
SimpleTemplateResponse.__init__(template, context=None, content_type=None, status=None, charset=None, using=None)[源代码]PInstantiates a SimpleTemplateResponse
object with the given template, context, content type, HTTP status, and
charset.
templateget_template()), the name of a template,
or a list of template names.contextdict of values to add to the template context. By default,
this is an empty dictionary.content_typeContent-Type header, including the
MIME type specification and the character set encoding. If
content_type is specified, then its value is used. Otherwise,
DEFAULT_CONTENT_TYPE is used.statuscharsetcontent_type, and if that is unsuccessful, the
DEFAULT_CHARSET setting will be used.usingSimpleTemplateResponse.resolve_context(context)[源代码]PPreprocesses context data that will be used for rendering a template.
Accepts a dict of context data. By default, returns the same
dict.
Override this method in order to customize the context.
SimpleTemplateResponse.resolve_template(template)[源代码]PResolves the template instance to use for rendering. Accepts a
backend-dependent template object (such as those returned by
get_template()), the name of a template,
or a list of template names.
Returns the backend-dependent template object instance to be rendered.
Override this method in order to customize template loading.
SimpleTemplateResponse.add_post_render_callback()[源代码]PAdd a callback that will be invoked after rendering has taken place. This hook can be used to defer certain processing operations (such as caching) until after rendering has occurred.
If the SimpleTemplateResponse
has already been rendered, the callback will be invoked
immediately.
When called, callbacks will be passed a single argument -- the
rendered SimpleTemplateResponse
instance.
If the callback returns a value that is not None, this will be
used as the response instead of the original response object (and
will be passed to the next post rendering callback etc.)
SimpleTemplateResponse.render()[源代码]PSets response.content to the result obtained by
SimpleTemplateResponse.rendered_content, runs all post-rendering
callbacks, and returns the resulting response object.
render() will only have an effect the first time it is called. On
subsequent calls, it will return the result obtained from the first call.
TemplateResponse objectsPTemplateResponse[源代码]PTemplateResponse is a subclass of
SimpleTemplateResponse that knows about
the current HttpRequest.
TemplateResponse.__init__(request, template, context=None, content_type=None, status=None, charset=None, using=None)[源代码]PInstantiates a TemplateResponse object
with the given request, template, context, content type, HTTP status, and
charset.
requestHttpRequest instance.templateget_template()), the name of a template,
or a list of template names.contextdict of values to add to the template context. By default,
this is an empty dictionary.content_typeContent-Type header, including the
MIME type specification and the character set encoding. If
content_type is specified, then its value is used. Otherwise,
DEFAULT_CONTENT_TYPE is used.statuscharsetcontent_type, and if that is unsuccessful, the
DEFAULT_CHARSET setting will be used.usingBefore a TemplateResponse instance can be
returned to the client, it must be rendered. The rendering process takes the
intermediate representation of template and context, and turns it into the
final byte stream that can be served to the client.
There are three circumstances under which a TemplateResponse will be
rendered:
TemplateResponse instance is explicitly rendered, using
the SimpleTemplateResponse.render() method.response.content.A TemplateResponse can only be rendered once. The first call to
SimpleTemplateResponse.render() sets the content of the response;
subsequent rendering calls do not change the response content.
However, when response.content is explicitly assigned, the
change is always applied. If you want to force the content to be
re-rendered, you can re-evaluate the rendered content, and assign
the content of the response manually:
# Set up a rendered TemplateResponse
>>> from django.template.response import TemplateResponse
>>> t = TemplateResponse(request, 'original.html', {})
>>> t.render()
>>> print(t.content)
Original content
# Re-rendering doesn't change content
>>> t.template_name = 'new.html'
>>> t.render()
>>> print(t.content)
Original content
# Assigning content does change, no render() call required
>>> t.content = t.rendered_content
>>> print(t.content)
New content
Some operations -- such as caching -- cannot be performed on an unrendered template. They must be performed on a fully complete and rendered response.
If you're using middleware, the solution is easy. Middleware provides multiple opportunities to process a response on exit from a view. If you put behavior in the response middleware, it's guaranteed to execute after template rendering has taken place.
However, if you're using a decorator, the same opportunities do not exist. Any behavior defined in a decorator is handled immediately.
To compensate for this (and any other analogous use cases),
TemplateResponse allows you to register callbacks that will
be invoked when rendering has completed. Using this callback, you can
defer critical processing until a point where you can guarantee that
rendered content will be available.
To define a post-render callback, just define a function that takes a single argument -- response -- and register that function with the template response:
from django.template.response import TemplateResponse
def my_render_callback(response):
# Do content-sensitive processing
do_post_processing()
def my_view(request):
# Create a response
response = TemplateResponse(request, 'mytemplate.html', {})
# Register the callback
response.add_post_render_callback(my_render_callback)
# Return the response
return response
my_render_callback() will be invoked after the mytemplate.html
has been rendered, and will be provided the fully rendered
TemplateResponse instance as an argument.
If the template has already been rendered, the callback will be invoked immediately.
TemplateResponse and SimpleTemplateResponsePA TemplateResponse object can be used anywhere that a normal
django.http.HttpResponse can be used. It can also be used as an
alternative to calling render().
For example, the following simple view returns a TemplateResponse
with a simple template and a context containing a queryset:
from django.template.response import TemplateResponse
def blog_index(request):
return TemplateResponse(request, 'entry_list.html', {'entries': Entry.objects.all()})
8月 23, 2019