django render_to_response - django

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.

Related

Why does Django need a request object in rendering a template?

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

How to use RequestContexts in render_to_response in Django 1.8

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))

Why does Django's render() function need the "request" argument?

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

My template is complaining that the context variable request.META.REQUEST_METHOD is missing. What are the possible causes?

The rendered template contains the following:
invalid context variable: 'request.META.REQUEST_METHOD'
I printed our locals() inside the view and I can clearly see
META:{
'REQUEST_METHOD': 'GET',
...
}
Any ideas on what could cause this ?
For your template to receive the request object, you will need to render the template with a RequestContext.
If you are using django.shortcuts.render_to_response something like the below:
return render_to_response(template_name, dictionary)
then you should note that, from the linked docs:
By default, the template will be rendered with a Context instance
and you will want to instead use the following construct:
return render_to_response(template_name, dictionary, context_instance=RequestContext(request))
However, better still would be to use django.shortcuts.render (introduced in Django 1.3) which uses a RequestContext by default, so you can just:
return render(request, template_name, dictionary)
It is possible that you are using render_to_response() without passing a context_instance argument.
Use render() instead and your problem should be gone.

How can I pass variables to a view using a context processor?

I am using a context processor to pass several variables to all my templates. However, I would also like use these variables in the actual views that render the respective templates. Should I add them to the session object of the request object or to the request object itself (if at all possible)?
Use RequestContext:
def my_view(request):
c = RequestContext(request)
# c['key'] gets the value for 'key' from your context processor.
return render_to_response('template.html', {}, context_instance = c)
Can't you just get a reference to the context processor and call it in your views? From what I read in the docs, there's nothing special about a context processor:
A context processor has a very simple interface: It's just a Python function that takes one argument, an HttpRequest object, and returns a dictionary that gets added to the template context. Each context processor must return a dictionary.
Custom context processors can live anywhere in your code base. All Django cares about is that your custom context processors are pointed-to by your TEMPLATE_CONTEXT_PROCESSORS setting.
You could have each view access them in the beginning, passing it the request parameter, or maybe create a decorator that would "inject" it in your views for you (whatever's easier in your case).