Question

I’m trying to POST some JSON and a binary file from an iPhone to a Django server running django-piston using ASIHTTPRequest

I know how to get it to work if I am ONLY sending JSON strings, and I know how to make it work if I am ONLY sending a file, but doing both is tricky.

So we’ll start with ASIHTTPRequest code

ASIFormDataRequest *request = [[ASIFormDataRequest alloc] initWithURL:url];

[request setRequestMethod:@"POST"];

[request setPostFormat:ASIMultipartFormDataPostFormat];

[request appendPostData:[@"{\"save\":{\"name\":\"iostest\"}}" dataUsingEncoding:NSUTF8StringEncoding]];

[request addData:UIImageJPEGRepresentation([UIImage imageNamed:@"test.jpg"], 1.0f)
    withFileName:@"test.jpg"
  andContentType:@"image/jpeg"
          forKey:@"data"];

[request setDelegate:self];

[request startAsynchronous];

My best idea here is that adding raw string data directly to the POST body and then adding a file just doesn’t work.

But if I instead try

[request setPostValue:@"{\"name\":\"iostest\"}" forKey:@"save"];

Then the piston data dictionary will store [‘save’] as a string instead of a deserialized object, so it will literally deliver the string

"{\"name\":\"iostest\"}"

Here’s my Piston handler code

def create(self, request):

     data = request.data

     print(data['save']) #{\"name\":\"iostest\"}"
     print("Files: " + request.FILES['data'].name) #test.jpg
     print("Data Save Name: " + data['save']['name']) #crash, interprets this as a string indeces lookup

Ideas are welcome.

Answer 1

I have basically hacked my way around this.

The basic problem is that the request format in which Django expects files to be submitted to the server is one which django-piston literally just drops the ball on.

When it encounters multipart requests, it simply doesn’t try to parse the data.

The solution to this problem is to manually call the parsing engine, which, in the case of JSON, is straight out of django.utils (which is kind of disappointing).

You achieve this by using ASIHTTPRequest (or the request module of your choice) to set a standard post value by key, and then access it the old fashioned way.

from django.utils import simplejson
data = simplejson.loads(request.POST['save'])

Which basically just reduces this handler method at this point to nothing more than a regular old Django view in terms of the steps you have to take to get it going.

So clearly, django-piston is not built to deal with files apparently?