Switch from NSURLConnection to NSURLSession in Objective-C

Question

I have this code in Objective-C which works with the initWithRequest of NSURLConnection class and Xcode gives me the following warning:

initWithRequest is deprecated: first deprecated in iOS9 - Use NSURLSession

My ViewController.m code is as follows:

NSString url = "my url"; 
NSMutableURLRequest *req = [NSMutableURLRequest requestWithURL:url];
conexion = [[NSURLConnection alloc]initWithRequest:req delegate:self];

Conexion is NSURLConnection in ViewController.h, so i was wondering how to switch from NSURLConnection to NSURLSession.

Answer 1

If you want to continue to use delegate-based API, like your current implementation, it's:

NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration defaultSessionConfiguration];
NSURLSession *session = [NSURLSession sessionWithConfiguration:configuration delegate:self delegateQueue:nil];

NSURL *URL = [NSURL URLWithString:string];

NSURLSessionTask *task = [session dataTaskWithURL:URL];
[task resume];

If you do that, you have to conform to NSURLSessionDelegate, NSURLSessionTaskDelegate, NSURLSessionDataDelegate methods, much like your current NSURLConnectionDataDelegate and NSURLConnectionDelegate methods.

By the way, I show dataTaskWithURL above, but if you really need to use NSURLRequest (e.g. you're going to do POST or other request), there is dataTaskWithRequest, too.

Having said that, using the completion handler rendition is much easier, saving you have having to write all of those delegate methods:

NSURLSession *session = [NSURLSession sharedSession];

NSURL *URL = [NSURL URLWithString:string];

NSURLSessionTask *task = [session dataTaskWithURL:URL completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
    // process response here
}];
[task resume];

If you do this, you don't have to implement any of those delegate methods. It's analogous to the NSURLConnection convenience method sendAsynchronousRequest, except it is cancellable.

And, just like the above dataTaskWithURL, there are also download and upload specific renditions, downloadTaskWithURL and uploadTaskWithRequest.

For more information, see Using NSURLSession in the URL Session Programming Guide.