NSURLSession delegate vs. completionHandler

问题:

I've always used completion handlers. With NSURLConnection and now with NSURLSession. It's led to my code being really untidy, especially I have request within request within request.

I wanted to try using delegates in NSURLSession to implement something I've done untidily with NSURLConnection.

So I created a NSURLSession, and created a dataTask:

NSURLSessionDataTask *dataTask = [overallSession dataTaskWithURL:url                                                   completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {                                                       if(error == nil)                                                       {                                                           NSString * text = [[NSString alloc] initWithData: data encoding: NSUTF8StringEncoding];                                                           NSLog(@"Data = %@",text);                                                       }                                                    }];      [dataTask resume]; 

Right now I have a completionHandler for the response, how would I switch to delegates to manage the response and data? And can I add another dataTask from the delegate of this one? Using the cookies that this dataTask created and placed into the session?

回答1:

If you want to add a custom delegate class, you need to implement the NSURLSessionDataDelegate and NSURLSessionTaskDelegate protocols at the minimum.

With the methods:

NSURLSessionDataDelegate - get continuous status of your request

 - (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveResponse:(NSURLResponse *)response  completionHandler:(void (^)(NSURLSessionResponseDisposition disposition))completionHandler {      receivedData=nil; receivedData=[[NSMutableData alloc] init];     [receivedData setLength:0];      completionHandler(NSURLSessionResponseAllow); } 

NSURLSessionDataDelegate

-(void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask    didReceiveData:(NSData *)data {      [receivedData appendData:data]; } 

NSURLSessionTaskDelegate

 - (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error {  if (error) {   // Handle error  } else {    NSDictionary* response=(NSDictionary*)[NSJSONSerialization JSONObjectWithData:receivedData options:kNilOptions error:&tempError];     // perform operations for the  NSDictionary response } 

If you want to separate the delegate code (middle layer) from your calling class (generally its good practice to have separate class/layer for network calls), the delegate of NSURLSession has to be :-

NSURLSession *session=[NSURLSession sessionWithConfiguration:sessionConfig delegate:myCustomDelegateClass delegateQueue:nil]; 

Ref Links:

1. NSURLSession Class Reference
2. iOS NSURLSession Example (HTTP GET, POST, Background Downlads )
3. From NSURLConnection to NSURLSession

文章来源: NSURLSession delegate vs. completionHandler