I'm working on a pretty big project right now where every view should be accessible via a normal request and an ajax request via the same url. I'm looking for ideas on how to create a small framework to handle this in a very generic way. Depending on if the view is called via ajax or not it needs to render a different template and return a json instead of a HttpResponse object. I'd like to collect any ideas on this topic - the main goal should be not to avoid the dry principle and make code that is as reusable as possible. I was already considering different options as generic views, decorators on views etc, but I'm open to anything. So please let me hear your suggestions or point me towards any readymade snippets you know!
This article seems to be quite a good tutorial on how to work with both ajax and regular requests. The request object has a method is_ajax() which will look for HTTP_X_REQUESTED_WITH: XMLHttpRequest. This will of course depend on these values being set correctly by the javascript sending the request.
From the article:
from django.http import HttpResponse
from django.core import serializers
from django.shortcuts import render_to_response
from your_app.models import ExampleModel
def xhr_test(request, format):
obj = ExampleModel.objects.all()
if request.is_ajax():
data = serializers.serialize('json', obj)
return HttpResponse(data,'json')
else:
return render_to_response('template.html', {'obj':obj}, context=...)
Or, you could use django-piston which is a RESTful framework for Django. I use this module in my project. You can define resources (sort of like views), and depending on either the mime-type or format passed to your url, it will emit either html, xml, or json. This will probably be the best way to go if every single view (or a large majority) need to be returned in different formats.
I have used a decorator for this. Have the view return the context, the template, and an alternate template.
If the Ajax version wants to return data, the third return value can be the data object to turn into JSON.
Related
I have read a lot of answers relating to how to dynamically add forms to an model formset in Django and can successfully implement that. However, I would now like to submit the formset with AJAX. This is mostly working now but I have an issue that I can't find a solution to in any other answer:
If you dynamically add a form to the formset, you give it a new form id number that is one larger than the maximum the form currently has and you also increment the management TOTAL_FORMS count by one. The newly added form then saves successfully as a new object.
I am trying to submit by AJAX so the user can continue editing without having the page refresh. The formset saves fine but any dynamically added forms are now existing objects. To account for this I need to increment the INITIAL_FORMS count on the management form when the save is successful. Easy enough. However, I've also realised I need to give the newly created objects an ID since they now exist in the database.
How can I get my view to tell me the ID of the new objects in its response to the AJAX call? Or is there a better way of looking at this?
Django forms and formsets are intended for classic browser-based posting of data. Though they can definitely be made to work with Javascript, the more you want to part from the normal behavior, the more complex it gets.
Depending on your requirements, you might start thinking about dropping it and switch to Javascript + REST endpoint. Of course, if you need progressive enhancements and you are required to have it work without javascript, that's not an option.
In any case, you want to have a customized view for posting from JS, so that you can get the result back and parse it easily in your AJAX handler. Probably some JSON.
There are several approaches you could take.
Have your AJAX send data to a different URL. This is pertinent if you have an API or are planning to build one at some point. So your form, when submitted normally, will do its old-style processing but your AJAX will talk to the API endpoint instead.
For instance, your form send to https://example.com/myform, but your Javascript code talks to REST api at https://example.com/api/v1/mymodel/ (sending PUT, POST and DELETE requests as appropriate).
Or if you don't have an API and building one seems overkill, you may just alter your view so it formats its output differently depending on whether the data is being submitted in the regular way or using AJAX.
You'd go about it like this:
class MyFormView(.....):
def render_to_response(self, context, **kwargs):
if self.request.is_ajax():
return self.render_to_json(context, **kwargs)
return super().render_to_response(context, **kwargs)
def render_to_json(context, **kwargs):
data = {
# see below!
}
return HttpResponse(
content=json.dumps(data).encode('ascii'),
content_type='application/json',
)
This is just an outline. You need to ensure is_ajax will detect it properly (see django doc). And you need to properly build data from context: extract the things you want to send back to your JS code and put them in the dict.
You will find it's manageable if you just do this for one, maybe two views in your project, but very quickly you'll want to have a small API instead, especially given how easy it is to build one with packages such as Django REST framework.
In your view, where you save the object, AFTER the save, the object.id will contain the new id for the object, which you can return via json or however you want in your ajax response, and then yes you will need to fill that into the formset row so that it will be submitted the next time.
One thing you have to watch out for is that django expects all existing rows to be at the top of the formset, and any new rows to be at the bottom. Otherwise, the formset save will complain about missing id's. So if you're doing any kind of sorting in your javascript, you can't do that.. unless you do quite a bit of fixing of all the field names etc in the formset. The formset code uses the numbers in the management form to determine which rows to insert and which rows to update, it does not do it on the basis of whether or not an id is present. Unfortunately...
I am new to Django but i am advanced programmer in other frameworks.
What i intend to do:
Press a form button, triggering Javascript that fires a Ajax request which is processed by a Django View (creates a file) that return plain simple JSON data (the name of the file) - and that is appended as a link to a DOM-Element named 'downloads'.
What i achieved so far instead:
Press the button, triggering js that fires a ajax request which is process by a Django view (creates a file) that return the whole page appended as a duplicate to the DOM-Element named 'downloads' (instead of simple JSON data).
here is the extracted code from the corresponding Django view:
context = {
'filename': filename
}
data['filename'] = render_to_string(current_app+'/json_download_link.html', context)
return HttpResponse(json.dumps(data), content_type="application/json")
I tried several variants (like https://stackoverflow.com/a/2428119/850547), with and without RequestContext object; different rendering strats.. i am out of ideas now..
It seems to me that there is NO possibility to make ajax requests without using a template in the response.. :-/ (but i hope i am wrong)
But even then: Why is Django return the main template (with full DOM) that i have NOT passed to the context...
I just want JSON data - not more!
I hope my problem is understandable... if you need more informations let me know and i will add them.
EDIT:
for the upcoming questions - json_download_link.html looks like this:
Download
But i don't even want to use that!
corresponding jquery:
$.post(url, form_data)
.done(function(result){
$('#downloads').append(' Download CSV')
})
I don't understand your question. Of course you can make an Ajax request without using a template. If you don't want to use a template, don't use a template. If you just want to return JSON, then do that.
Without having any details of what's going wrong, I would imagine that your Ajax request is not hitting the view you think it is, but is going to the original full-page view. Try adding some logging in the view to see what's going on.
There is no need to return the full template. You can return parts of template and render/append them at the frontend.
A template can be as small as you want. For example this is a template:
name.html
<p>My name is {{name}}</p>
You can return only this template with json.dumps() and append it on the front end.
What is your json_download_link.html?
assuming example.csv is string
data ={}
data['filename'] = u'example.csv'
return HttpResponse(simplejson.dumps(data), content_type="application/json")
Is this what you are looking for?
Could somebody please suggest me a good beginner tutorial of using Ajax with Zend 1.I have been searching the net for some of this tutorials, but couldn't find an understandable one.In some they say you have to create a .json.phtml file for json response, the others don't.I am very confused about all these ajax calls with Zend Framework 1. Would be very grateful.
Well there really are some basic things.
Get your data (from DB, file, in-code array, whatever)
Get the controller helper
Send the JSON response
And that's it. OK, not exactly but basically yes!
Provided you have the data in $data:
$this->_helper->json($data, true);
will return a JSON response. The documentation is here.
Now there is the other notion of a Context Switch and AjaxContentHelper which:
The ContextSwitch action helper is intended for facilitating returning different response formats on request. The AjaxContext helper is a specialized version of ContextSwitch that facilitates returning responses to XmlHttpRequests.
To enable either one, you must provide hinting in your controller as to what actions can respond to which contexts. If an incoming request indicates a valid context for the given action, the helper will then:
Disable layouts, if enabled.
Set an alternate view suffix, effectively requiring a separate view script for the context.
Send appropriate response headers for the context desired.
Optionally, call specified callbacks to setup the context and/or perform post-processing.
Something like this:
$contextSwitch = $this->_helper->getHelper('contextSwitch');
$contextSwitch->setDefaultContext('json');
$contextSwitch->addActionContext('index', array('xml','json'))->initContext();
$contextSwitch->addActionContext('get', array('xml','json'))->initContext();
$contextSwitch->addActionContext('post', array('xml','json'))->initContext();
$contextSwitch->addActionContext('put', array('xml','json'))->initContext();
$contextSwitch->addActionContext('delete', array('xml','json'))->initContext();
$contextSwitch->addActionContext('head', array('xml','json'))->initContext();
You don't really need a tutorial I think. All you need is a good basic knowledge of how the web works internally and to read the Zend Documentation. Anyway here is some tutorial on ContextSwitch.
If i have a link like this one Get User Data who points in a view inside my own server, is there any way to send a json object (maybe just maybe with ajax?) to another external server and retrieve an answer? Something like this:
from django.shortcuts import render
def profile(request):
#send a json object to another server like http://www.myotherserver.com/user
#get the answer and process it
return render(request, 'accounts/profile.html' ,
{'profile_user': data_from_the_external_server})
The above i can implement it of course with jquery-ajax but i just was wondering if i can do it this way...
Thanks in advance.
Of course you can. Why wouldn't it be possible?
Don't code this in AJAX if that's not necessary.
There are 2 things you need, you need to prepare the JSon to send and then you need to send it to the API you want:
Look at "simplejson" to create the json data to send.
Look at "urllib" to send a request to another server in Python (like here: How to send a POST request using django?)
Also do not put it straight in your view. Create a new class for it. So in your view you'll have something like that:
def profile(request):
# instantiate your service here (better with DI)
profile_user = my_service.get_profile_user()
return render(
request,
'accounts/profile.html' ,
{
'profile_user': profile_user
}
)
If you need to send HTTP data (via a POST or GET) to another server and receive a result from within your view, you can use Python's urllib2 library. However there is an easier third party library called Requests which can handle this task for you.
I would develop my CakePHP application in the most reusable way. I'd like to treat it as webservices, so I don't want to strictly bind controller with view. My idea is: controller just returns json info, the view calls the controller and get the json and make html output.
How can I realize that? Could be a good approch, developing pages rather than views, and inside that pages call the webservices previously developed.
You can even forget about creating view files, using $this->set('_serialize', array('people')); in your PeopleController::show()
Well Cake is kinda' works like this "out of the box". You can use Router::parseExtensions(); to define what type of data you would like to serve. For example in app/Config/routes.php:
Router::parseExtensions('xml','json');
This will make it possible to detect what kind of request is incoming. For example if someone requests:
www.example.com/people/list.json or www.example.com/people/list.xml, in your PeopleController's list() method you'd be able to detect what kind of resource is being requested - json or xml, or of course any other
extension you define. This is what the RequestHandlerComponent is used for. You can check if it is xml for example:
if($this->RequestHandler->isXml()) {
//Some code
}
The different extensions are only different representation of the data, so it shouldn't matter what exactly you're serving. From v2.1 Cake will automatically switch the view class when it sees a JSON or XML request, which takes us to the new JSON and XML views.
All you will have to do is provide the views in the appropriate places.
In View/People (as for this example) you would have:
..View/People/
list.ctp
xml/
list.ctp - XML view
json/
list.ctp - JSON view