Why does Django need a request object in rendering a template?
return render(request, 'polls/index.html', context)
As per the docs about render:
Combines a given template with a given context dictionary and returns
an HttpResponse object with that rendered text.
Thus it's meant to be used in views, where you have a request object and need to return an HttpResponse. A typical use case is when you build the context from the request.
If you only need to render a template, you can use the shortcut function render_to_string:
from django.template.loader import render_to_string
render_to_string('your_template.html', {'some_key':'some_value'})
Or do it manually:
from django.template import Context, Template
Template('your_template.html').render(Context({'some_key':'some_value'})
The request argument is used if you want to use a RequestContext which is usually the case when you want to use template context processors. You can pass in None as the request argument if you want and you will get a regular Context object in your template.
I believe this is b/c the render() shortcut is using a RequestContext
You could also use get_template directly and call render with a normal Context
Related
Suppose, we have a url path:
path('something/<int:some_param>/test/', views.some_view)
When a user hits this url, django makes an instance of HttpRequest, that will be passed to the some_view view. Is there a way to get the some_param url parameter from the request object outside the some_view code? (for instance, to do some processing that depends on some_param in a custom middleware).
One possible solution is to parse the HttpRequest.path attribute, but is there any prebuilt way to do this?
Django calls your view with the request object and some_param, which you have access to inside views.some_view. Your function will have the following signature:
def some_view(request, some_param):
....
Or:
def some_view(request, **kwargs):
some_param=kwargs.get('some_param', None)
You can then use some_param inside your view to do whatever you need to do with it, save it in a database, put it in a cookie, do calculations with it, get some database data with it, etc. Then once you're done, you need to return a response object. Usually by calling render or TemplateResponse with a template or returning HttpResponse without a template. You render templates providing a context dictionary which you are free to put anything you like into (like some_param), which makes it available to be rendered in your HTML template. That rendered HTML template is then returned as response to your user through the magic of the render function or TemplateResponse class, which ends the view process. I.e. like so:
return TemplateResponse(request, 'template.html', context)
To store some_param in between views, you'll need to save it in the database, store it in the user's session, or use a cookie. Or pass it to the next view inside the url or outside the url via /?param=some_param. Without saying what you need some_param for later on, it's hard to solve your issue.
The one possible solution here is to use the resolve function from django.urls module. It is extremely uselful if you want to access the URL parameters from URL path that is related to a HttpRequest object outside a view function. For example, get the URL params and process them in the custom middleware or other parts of your code.
Example:
from django.urls import resolve
...
func, args, kwargs = resolve(some_request.path)
I understand things have changed in Django 1.8 with how render_to_response
takes arguments. I have lots of views and use this pattern everywhere:
...return render_to_response( template, context,
context_instance=MyRequestContext(request))
MyRequestContext extends the RequestContext and adds some paramaters I always use in my templates.
Now this no longer works, and values in MyRequestContext is no longer accessible in the templates anymore.
So how should RequestContext be use now in Django 1.8? I need them + some context passed to all my templates.
/ J
-- EDIT --
Thanks for all the answers, as you point out this should work...
I ended up rewriting and replacing my previous subclassing of RequestContext --> MyRequestContext w. doing a separate ContextProcessors function and adding this into my OPTIONS:context_processors list and then using a normal RequestContext(request) in all of my views. Not sure what bug/problem I had in old solutions but this works now. Again - thanks for inspiration and responses.
You can manually fetch the template and render it to a HttpResponse object:
from django.template.loader import get_template
from django.http import HttpResponse
template = get_template(template_name)
context = MyRequestContext(request, context_dict)
return HttpResponse(template.render(context))
I bumped into this as well and had to read the docs on render_to_response a couple of times.
The thing that confused me is the example code in combination with the deprecation warning:
return render_to_response('my_template.html',
my_context,
context_instance=RequestContext(request))
Deprecated since version 1.8: The context_instance argument is
deprecated. Simply use context.
Note that context_instance is still used at many examples in the documentation and it is okay to use it that way until Django 2. I don't want to wait until I'm forced to change when I upgrade so...
I moved my_context dict out of render_to_response into the RequestContext class. I believe this must be the new style:
return render_to_response('template.html',
context=RequestContext(request, my_context))
Context is the second argument, so you don't even have to name it:
return render_to_response('template.html',
RequestContext(request, my_context))
Sorry for what might be a silly question, but why is the request argument mandatory in the render() function?
The render() shortcut renders templates with a request context. Template context processors take the request object and return a dictionary which is added to the context.
A common template context processor is the auth context processor, which takes the request object, and adds the logged-in user to the context.
If you don't need to render the template with a request context, you can use request=None.
def my_view(request):
return render(None, "my_template.html", {'foo': 'bar'})
For rendering a template outside of the context of a view (i.e. without a request object), one can use render_to_string():
from django.template.loader import render_to_string
render_to_string('path/to/template.html', context={'key': 'val'})
In django render is used for loading the templates.So for this we
import-from django.shortcuts import render
its a template shortcut.
Rendering is the process of gathering data (if any) and load the associated templates
I'm putting
...}, context_instance=RequestContext(request))
at the end of all my render_to_response's. I'm sure this is not right. Can anyone tell me when I should be using these?
If you are using Django 1.3 you can use the render() shortcut function so you don't have to explicitly write context_instance=RequestContext(request) for each view .
Combines a given template with a given
context dictionary and returns an
HttpResponse object with that rendered
text.
render() is the same as a call to
render_to_response() with a
context_instance argument that forces
the use of a RequestContext.
You are doing it "right". This means that all of the Context Processors will run on this view, and you will have access to all of the juicy bits in your template.
The other way to do this is to use direct_to_template, which saves you having to instantiate a RequestContext object, but has the same outcomes.
so I was wondering if you could return an inclusion tag directly from a view.
The page is a normal page with a list of items. The list of items is rendered using an inclusion tag. If an ajax request is made to the view, I want to return only what the inclusion tag would return so I can append it onto the page via javascript. Is something like this possible? Or should I architect this better?
This sounds like a job for the render_to_string or render_to_response shortcuts:
https://docs.djangoproject.com/en/dev/ref/templates/api/#the-render-to-string-shortcut
https://docs.djangoproject.com/en/dev/topics/http/shortcuts/#django.shortcuts.render_to_response
We can still use the inclusion tag to generate a template context dict from our args (as helpfully pointed out by #BobStein-VisiBone in comments)
from django.template.loader import render_to_string
from django.shortcuts import render_to_response
from .templatetags import my_inclusion_tag
rendered = render_to_string('my_include.html', my_inclusion_tag(foo='bar'))
#or
def my_view(request):
if request.is_ajax():
return render_to_response('my_include.html',
my_inclusion_tag(foo='bar'),
context_instance=RequestContext(request))
quick and dirty way could be to have a view, that renders a template, that only contains your templatetag.
I was trying to do the exact same thing today, and ended up writing a helper function to render template tags:
def render_templatetag(request, tag_string, tag_file, dictionary=None):
dictionary = dictionary or {}
context_instance = RequestContext(request)
context_instance.update(dictionary)
t = Template("{%% load %s %%}{%% %s %%}" % (tag_file, tag_string))
return t.render(context_instance)
tag_string is the call to the template tag as it'd appear in a normal template, and tag_file is the file you need to load for the template tag.
This is certainly possible. A view can render any template that an inclusion tag can. The advantage of this approach is that you can leverage the full strength of Django's templates.
On the other hand AJAX responses typically do not contain HTML so much as XML/JSON. If you are using Django's template features you are better off with returning HTML. If not, XML/JSON might make more sense. Just my two cents.
Using inclusion tag with configurable template decorator provided by Gonz instead of default Django's inclusion tags you can write a helper in your view:
from django.template.loader import render_to_string
from home.templatetags.objectwidgets import object_widget
def _object_widget(request, obj):
template, context = object_widget(RequestContext(request), obj)
return render_to_string(template, context)
It's DRY and works with Django 1.3 (I haven't tested it with Django 1.4).
I use this technique to return search results rendered in HTML via JSON/AJAX calls (nothing better which I came up with).
It's possible, but probably bit hacky, complex or complicated.
What I would suggest, is architect it so that you have the rendering part in utils.py function and use it in a simple_tag instead of an inclusion_tag. This way you can then use the same utils rendering function easily in views.
In my (very simplified) imaginary example I have listing of users and a "Load more" button that returns more users.
account/utils.py
from django.template.loader import render_to_string
def render_users(users):
return render_to_string("account/user_list_items.html", {"users": users})
account/templatetags/account_tags.py
from django import template
from ..utils import render_users
register = template.Library()
#register.simple_tag
def list_users(users):
return render_users(users)
account/views.py
from django.http import HttpResponse
from .models import User
from .utils import render_users
def load_more_users(request):
limit = request.GET["limit"]
offset = request.GET["offset"]
users = User.objects.all()[offset:offset + limit]
return HttpResponse(render_users(users))
Simple is better than complex.