Restkit : multipartFormRequestWithObject not json - json

Question

I am using RestKit 2.0 to send a core data entity and an image to a server with the 'multipartFormRequestWithObject' method. However, when the entity data arrives it is not in json format. If I send the entity using 'postObject' without an image then the data is in json format. I use the same RKObjectMapping for both situations.
What do I have to do to make the Object serialize to json? I tried
[request setValue:#"application/json" forHTTPHeaderField:#"content-type"];
But that didn't help and I already have my object manager settings as so:
[objectManager setRequestSerializationMIMEType:RKMIMETypeJSON];
[objectManager setAcceptHeaderWithMIMEType:RKMIMETypeJSON];
My Header Content-Type is multipart/form-data but I guess that is required.
request.headers={
Accept = "application/json";
"Accept-Language" = "en;q=1, fr;q=0.9, de;q=0.8, zh-Hans;q=0.7, zh-Hant;q=0.6, ja;q=0.5";
"Accept-Version" = 1;
"Content-Length" = 19014;
"Content-Type" = "multipart/form-data; boundary=Boundary+0xAbCdEfGbOuNdArY";
"User-Agent" = "app/1.0 (iPhone Simulator; iOS 7.0; Scale/2.00)";
}
My complete code is for the mapping and operation are below. As usual any feedback would be great. Thanks. Al
- (void)loginMainUser:(NSDictionary*)paramsDict path:(NSString *)apiPath{
RKObjectManager *manager = [RKObjectManager sharedManager];
// Response Mapping
RKObjectMapping *mapping = [RKObjectMapping mappingForClass:[self class]];
[mapping addAttributeMappingsFromDictionary:#{#"token" : #"token",
#"_links" : #"links"}];
[manager addResponseDescriptorsFromArray:#[[RKResponseDescriptor responseDescriptorWithMapping:mapping
method:RKRequestMethodAny
pathPattern:nil
keyPath:nil
statusCodes:RKStatusCodeIndexSetForClass(RKStatusCodeClassSuccessful)]]];
// Request Mapping
RKObjectMapping *userRequestMapping = [RKObjectMapping requestMapping];
[userRequestMapping addAttributeMappingsFromDictionary:#{#"name" : #"first_name",
#"surname" : #"last_name",
#"email" : #"email",
#"password" : #"password"}];
RKRequestDescriptor *requestDescriptor = [RKRequestDescriptor requestDescriptorWithMapping:userRequestMapping
objectClass:[self class]
rootKeyPath:nil
method:RKRequestMethodAny];
[manager addRequestDescriptor:requestDescriptor];
UIImage *image = [UIImage imageNamed:#"logo.png"];
// Serialize the Article attributes then attach a file
NSMutableURLRequest *request = [manager multipartFormRequestWithObject:self
method:RKRequestMethodPOST
path:apiPath
parameters:nil
constructingBodyWithBlock:^(id<AFMultipartFormData> formData) {
[formData appendPartWithFileData:UIImagePNGRepresentation(image)
name:#"logo"
fileName:#"logo.png"
mimeType:#"image/png"];
}];
RKObjectRequestOperation *operation = [manager objectRequestOperationWithRequest:request
success:^(RKObjectRequestOperation *operation, RKMappingResult *mappingResult) {
NSLog(#"Success");
} failure:^(RKObjectRequestOperation *operation, NSError *error) {
NSLog(#"Failed");
}];
[manager enqueueObjectRequestOperation:operation];
}

Answer 1

multipartFormRequestWithObject is explicitly not JSON. This is by design. It's the HTTP content type that is changed so JSON and multipart form are mutually exclusive.
So, you need to change your mind about what you're trying to achieve.
One option could be to use a mapping operation to create the JSON for your object and then supply that JSON when you call multipartFormRequestWithObject. This would give you a multipart form message being sent with a section of JSON that could be deserialised on the server.

Answer 2

It is not the best approach but if you really need to get the JSON from a object with RestKit, you can convert it using this code:
// The object you want to convert
YourObject *object = ...;
// The RestKit descriptor that you want to use to map.
RKRequestDescriptor *requestDescriptorObject = ...;
NSDictionary *parametersForObject;
parametersForObject = [RKObjectParameterization parametersWithObject:object
requestDescriptor:requestDescriptorObject
error:nil];
NSData *jsonData = [NSJSONSerialization dataWithJSONObject:parametersForObject
options:NSJSONWritingPrettyPrinted
error:nil];
NSString *jsonString;
if(jsonData) {
jsonString = [[NSString alloc] initWithData:jsonData
encoding:NSUTF8StringEncoding];
}
And then with the JSON string you can post it in a multi-part post. It can be done with any method, but as you have already RestKit, you can do it with the library.
For example, at the code of below there is a post of a file and the JSON string (in fact, the JSON data).
// The RestKit manager
RKObjectManager *manager = ...;
// The server endpoint
NSString *path = ...;
NSMutableURLRequest *request = [manager multipartFormRequestWithObject:nil method:RKRequestMethodPOST path:path parameters:nil constructingBodyWithBlock:^(id<AFMultipartFormData> formData) {
// Post of the file
[formData appendPartWithFileData:[NSData dataWithData:self.dataFile]
name:#"file"
fileName:filename
mimeType:mimetype];
// Post of the JSON data
[formData appendPartWithFormData:jsonData name:#"json_data"];
}];