box file upload api from iOS is not working

Question

I am trying to upload a file to a box account using box's HTTP API (not iOS SDK), but for some reason its not working and returning status code 400. What is my mistake in the following code?

NSString *uploadURL = @"https://upload.box.com/api/2.0/files/content";
NSURLSessionConfiguration *config = [NSURLSessionConfiguration defaultSessionConfiguration];

NSURLSession *upLoadSession = [NSURLSession sessionWithConfiguration:config delegate:self delegateQueue:nil];

NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:[NSURL URLWithString:uploadURL]];
[request setHTTPMethod:@"POST"];

[request addValue:[NSString stringWithFormat:@"Bearer %@", @"box_access_token_here"] forHTTPHeaderField:@"Authorization"];

NSString *boundary = @"some_random_boundary_value";
NSString *contentType = [NSString stringWithFormat:@"multipart/form-data; boundary=%@", boundary];
[request addValue:contentType forHTTPHeaderField:@"Content-Type"];
NSMutableData *body = [NSMutableData data];

[body appendData:[[NSString stringWithFormat:@"--%@\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[@"Content-Disposition: form-data; name=\"attributes\"\r\n\r\n" dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[@"Content-Type: application/json\r\n\r\n" dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:@"'{\"name\":\"%@\", \"parent\":{\"id\":\"%@\"}}'", @"file_name", @"box_folder_id"] dataUsingEncoding:NSUTF8StringEncoding]];

[body appendData:[[NSString stringWithFormat:@"\r\n--%@\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[@"Content-Disposition: form-data; name=\"file\"\r\n" dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:@"Content-Type: %@\r\n\r\n", @"mime_type"] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:UIImageJPEGRepresentation(someUIImage, 1.0)];

[body appendData:[[NSString stringWithFormat:@"\r\n--%@--\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];
[request setValue:[NSString stringWithFormat:@"%lu", (unsigned long)body.length] forHTTPHeaderField:@"Content-Length"];
[request setHTTPBody:body];

NSURLSessionUploadTask *uploadTask = [upLoadSession uploadTaskWithRequest:request fromData:body completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
    if (error) {
        NSLog(@"%@", error.debugDescription);
    } else {
        NSLog(@"%@", @"Successfully uploaded");
    }
}];

[uploadTask resume];

Answer 1

I'm not sure what is wrong with code but I was getting the same 400 Bad Request when tried to implement upload in the way it's described here https://box-content.readme.io/#upload-a-file.

I ended up replicating behavior that Android sample code uses - and it's somewhat different from what is in API docs:

Content-Type: multipart/form-data; boundary=dcf6d5da-6b79-4d80-8503-9ca17037e7c3
Content-Length: 757
--dcf6d5da-6b79-4d80-8503-9ca17037e7c3
Content-Disposition: form-data; name="parent_id"
Content-Type: text/plain; charset=UTF-8
Content-Length: 10
Content-Transfer-Encoding: binary

3973764013
--dcf6d5da-6b79-4d80-8503-9ca17037e7c3
Content-Disposition: form-data; name="filename"; filename="your-file-name"
Content-Type: text/html
Content-Length: 300
Content-Transfer-Encoding: binary

your file binary content goes here
--dcf6d5da-6b79-4d80-8503-9ca17037e7c3--

Please note how parent_id and filename parts are used - this is quite in contrast to what is advices in API docs.