Objective-c : How method using block can returns object

Question

I have a method that should return a dict:

-(NSDictionary *) searcherMethod: (NSString *) text {

         [ReadService readFromApi:APIURL

                 whenFinish:^(id responseObject) {

                //HERE I have A response from API
                NSDictionary *response = (NSDictionary*)responseObject;

               //HOW  searcherMethod can return the response dict?
              return response;
          }];        
}

How make that searcherMethod can return the response dict?

Correct answer would be: since it is an asynchronous request, you should manage the asynchronous response in your code. A quick solution for what you want to achieve: use a synchronous request, but it will block your application for duration of the request itself - if executed on the main thread. — Marco Pace, May 28 '18 at 07:49
Possible duplicate of [How do I wait for an asynchronously dispatched block to finish?](https://stackoverflow.com/questions/4326350/how-do-i-wait-for-an-asynchronously-dispatched-block-to-finish) — FreeNickname, May 28 '18 at 07:52

MobileMatrix · Answer 1 · 2018-05-28T08:23:14.617

The response from the API call return asynchronously, so you have to write block for return the result while you have got the response from API.

The below code help you to achieve your requirements.
This code will return response asynchronously

-(void) searcherMethod: (NSString *) text  responseCompletion:(void (^_Nullable)(NSDictionary *))responseCompletion{

    [ReadService readFromApi:APIURL

                  whenFinish:^(id responseObject) {

                      //HERE I have A response from API
                      NSDictionary *response = (NSDictionary*)responseObject;

                      //HOW  searcherMethod can return the response dict?
                      if (responseCompletion) {
                          responseCompletion(response);
                      }
                  }];
}

This code will return response synchronously

-(NSDictionary *) searcherMethod: (NSString *) text  {

    NSDictionary *response = nil;
    // create the semaphore for synchronously call
    dispatch_semaphore_t semaphore = dispatch_semaphore_create(0);

    [ReadService readFromApi:APIURL

                  whenFinish:^(id responseObject) {

                      //HERE I have A response from API
                      response = (NSDictionary*)responseObject;

                      // fire signal for semaphore so your code will execute further
                      dispatch_semaphore_signal(semaphore);
                  }];
    dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
    return response;
}

Semaphore is blocking the execution until the signal is not received, this will return your method after receiving the response.
you can use below code for the method call.

[self searcherMethod:@"responseText" responseCompletion:^(NSDictionary *responseDict) {
        //result
        NSLog(@"Response : %@",responseDict);
    }];

Now you can call your method synchronously

NSDictinary *response = [self searcherMethod:text]

Hope this will help you.

thanks. But I need response dict outside block, i.e. respose = [self searcherMethod:text] — doxsi, May 28 '18 at 07:45
@doxsi I have updated the answer check let me know it is working for you or not. — MobileMatrix, May 28 '18 at 08:27

Objective-c : How method using block can returns object

1 Answers1