Setting CURL Arguments in NSURLSession - objective-c

Question

I am trying to execute the following CURL command in a Mac app in Objective-C:
curl -u [USERNAME]:[PASSWORD] -X POST --limit-rate 40000 --header "Content-Type: audio/wav” --header "Transfer-Encoding: chunked" --data-binary #/Users/name/Desktop/test.wav "https://stream.watsonplatform.net/speech-to-text/api/v1/recognize?continuous=true"
I am unsure how to set the various CURL arguments in an NSURLSession. I think I set the HTTP headers correctly, but I don't know how to set the u, limit-rate, and data-binary arguments. This is what I have so far:
NSString* credentials = #"[USERNAME]:[PASSWORD]";
NSString* audioPath = #"#/Users/name/Desktop/test.wav";
NSString* fullPath = #"https://stream.watsonplatform.net/speech-to-text/api/v1/recognize?continuous=true";
NSURL* fullURL = [NSURL URLWithString: fullPath];
NSURLSessionConfiguration* sessionConfig = [NSURLSessionConfiguration
defaultSessionConfiguration];
[sessionConfig setHTTPAdditionalHeaders: #{#"Content-Type" : #"audio/wav",
#"Transfer-Encoding": #"chunked"}];
NSMutableData* body = [[NSMutableData alloc] init];
[body appendData: [[NSString stringWithFormat: #"u: %#", credentials]
dataUsingEncoding: NSUTF8StringEncoding]];
[body appendData: [#"limit-rate: 40000" dataUsingEncoding: NSUTF8StringEncoding]];
[body appendData: [[NSString stringWithFormat: #"data-binary: %#", audioPath]
dataUsingEncoding: NSUTF8StringEncoding]];
NSURLSession* urlSession = [NSURLSession sessionWithConfiguration: sessionConfig];
NSMutableURLRequest* urlRequest = [NSMutableURLRequest requestWithURL: fullURL];
[urlRequest setHTTPBody: body];
[urlRequest setHTTPMethod: #"POST"];
NSURLSessionDataTask* dataTask = [urlSession dataTaskWithRequest: urlRequest
completionHandler: ^(NSData* data,
NSURLResponse* response,
NSError* error) {
if (nil == error)
{
if (0 != [data length])
{
// Do something with the returned JSON
}
else
NSLog(#"Data Error: Data is nil or data length is 0.");
}
else
NSLog(#"%#", error);
}];
[dataTask resume];
The error I am getting when I run this code is:
Error Domain=NSCocoaErrorDomain Code=3840 "JSON text did not start with array or object and option to allow fragments not set." UserInfo={NSDebugDescription=JSON text did not start with array or object and option to allow fragments not set.}
Does anybody have any ideas? I think it's not working because I'm setting the CURL arguments incorrectly.
Thanks in advance!

Answer 1

The NSURL family of APIs has no mechanism for rate limiting. If that's a requirement, you'll have to use libcurl instead. If not, then:
The body should be the contents of the file (use NSData's dataWithContentsOfURL: method) and nothing else.
The authentication is too complicated to explain here.
One approach is using the techniques described Apple's URL Session Programming Guide, which describes how to do HTTP authentication in depth.
However, the easiest way, by far, to do auth with NSURL* APIs is to just add an Internet password into the keychain, as described in APple's Keychain Services Concepts.