Upload image from iOS to Django - ios

Question

I need help getting a basic understanding of uploading a file to a Django view via a post request. This is the Django form I'd like to upload the image to:
https://domfa.de/upload_profile/
This is the views.py code for this exact Django view URL:
def profile_picture(request):
if request.POST:
form = UserProfileForm(request.POST, request.FILES)
obj = form.save(commit=False)
obj.user_id = request.user.id
obj.profile_picture = obj.profile_picture
obj.save()
return render_to_response('profile.html', args, RequestContext(request))
else:
formNew = UserProfileForm()
args = {}
args.update(csrf(request))
args['uid'] = request.user.id
args['form'] = formNew
return render_to_response('profile.html', args, RequestContext(request))
And the actual form for this is extremely simple with just a single field for the actual profile picture:
class UserProfileForm(forms.ModelForm):
class Meta:
model = UserProfile
fields = ('profile_picture',)
def __init__(self, *args, **kwargs):
super(UserProfileForm, self).__init__(*args, **kwargs)
So the Django side works great, I'm always able to upload an image successfully as long as I'm logged in. I'm stuck though however on how to POST an image to this extremely simple Django view, I've already logged in to the Django server as a user using a separate NSUrl request:
UIImage *picture = [UIImage imageNamed:#"myFile.png"];
NSData *imageData = UIImagePNGRepresentation(picture);
NSMutableURLRequest *request = [[NSMutableURLRequest alloc]
initWithURL:[NSURL
URLWithString:#"https://domfa.de/upload_profile/"]];
[request setHTTPMethod:#"POST"];
[request setValue:#"image/png" forHTTPHeaderField:#"Content-type"];
[request setHTTPBody:imageData];
NSData *returnData = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
NSLog(#"%#", returnData);
So assuming all the Django code works, which it does, what's wrong with my objective-c code which does the actual image uploading?
And also, how could I get response messages from the server in the NSLog so I could better know why the server won't accept a file POST request?

Answer 1

Getting feedback what is going on when sending a HTTP request from iOS
The problem is that you are not passing in a pointer to a NSURLResponse object which you could examine after the request was made.
NSURLResponse *response;
NSData *returnData = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:nil];
Now you can examine the output by looking at the object.
Why is it not uploading?
There are several issues with your approach: You are using django's forms API which is OK, but there are two pitfalls in your code:
CSRF You are not setting the the CSRF value correctly when submitting the form. You can workaround it by first accessing your form with a GET request, just like a browser would do it, then get the CSRF token from the cookies which the server set and then sending a POST request including the retrieved CSRF token. See also CSRF handling in AJAX requests
Data encoding You are not sending form data back to the view, but raw data instead. This will not work this way. You would have to send proper POST form data. You could do it manually or use ASIHTTPRequest which abstracts the cumbersome handling of multipart/form-data.
I would rethink the design decision to use a form to programatically upload a picture. Why not use something more like a REST API for this? There are great frameworks for implementing a clean REST API in django (e.g. http://tastypieapi.org/).
Maybe looking at the API description of Twitter and app.net could help inspiring you how to build this.