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
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)
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
I want to write custom template loader for my Django app which looks for a specific folder based on a key that is part of the request.
Let me get into more details to be clear. Assume that I will be getting a key on every request(which I populate using a middleware).
Example: request.key could be 'india' or 'usa' or 'uk'.
I want my template loader to look for the template "templates/<key>/<template.html>". So when I say {% include "home.html" %}, I want the template loader to load "templates/india/home.html" or "templates/usa/home.html" or "templates/uk/home.html" based on the request.
Is there a way to pass the request object to a custom template loader?
I've been searching for the same solution and, after a couple days of searching, decided to use threading.local(). Simply make the request object global for the duration of the HTTP request processing! Commence rotten tomato throwing from the gallery.
Let me explain:
As of Django 1.8 (according to the development version docs) the "dirs" argument for all template finding functions will be deprecated. (ref)
This means that there are no arguments passed into a custom template loader other than the template name being requested and the list of template directories. If you want to access paramters in the request URL (or even the session information) you'll have to "reach out" into some other storage mechanism.
import threading
_local = threading.local()
class CustomMiddleware:
def process_request(self, request):
_local.request = request
def load_template_source(template_name, template_dirs=None):
if _local.request:
# Get the request URL and work your magic here!
pass
In my case it wasn't the request object (directly) I was after but rather what site (I'm developing a SaaS solution) the template should be rendered for.
To find the template to render Django uses the get_template method which only gets the template_name and optional dirs argument. So you cannot really pass the request there.
However, if you customize your render_to_response function to pass along a dirs argument you should be able to do it.
For example (assuming you are using a RequestContext as most people would):
from django import shortcuts
from django.conf import settings
def render_to_response(template_name, dictionary=None, context_instance=None, content_type=None, dirs):
assert context_instance, 'This method requires a `RequestContext` instance to function'
if not dirs:
dirs = []
dirs.append(os.path.join(settings.BASE_TEMPLATE_DIR, context_instance['request'].key)
return shortcuts.render_to_response(template_name, dictionary, context_instance, content_type, dirs)
I have been trying to use the updated yourlabs subscription example, and the installation has worked fine except that
Each of the views in the subscription app returns the request variable in the render to template.
this request context variable is not received in the template and as a result I am getting the following error
Caught VariableDoesNotExist while rendering: Failed lookup for key [request] in u
Since this is being returned in every view I can't solve this problem by making some tweaks in a particular template
This is happening because request isn't in your template's context and the template is using some template code that expected it to be there. That code (e.g. a custom template tag) should better handle VariableDoesNotExist
In addition, your views probably shouldn't return request in every response explicitly. Let Django handle this for you.
To do this, add the request template context processor that ships with Django to your TEMPLATE_CONTEXT_PROCESSORS:
TEMPLATE_CONTEXT_PROCESSORS = (
...
'django.core.context_processors.request',
...
)
If you are already using this template context processor, ensure that render_to_response is called with context_instance=RequestContext(request) as the final argument (the below example is from the docs):
def some_view(request):
# ...
return render_to_response('my_template.html',
my_data_dictionary,
context_instance=RequestContext(request))
This ensures that all the dicts returned by the template context processors in TEMPLATE_CONTEXT_PROCESSORS are passed to the template.
You could also use the rendershortcut, which will automatically render the template with an instance of Requestcontext.
Another option added in Django 1.3 is the TemplateResponse, which will also use an instance of RequestContext.
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.