Question

I need to encapsulate the response from AFNetworking calls within my own method as I’m writing a library. This code gets me close:

MyDevice *devices = [[MyDevice alloc] init];
  [devices getDevices:@"devices.json?user_id=10" success:^(AFHTTPRequestOperation *operation, id responseObject) {

    ... can process json object here ...

}

 - (void)getDevices:(NSString *)netPath success:(void (^)(AFHTTPRequestOperation *operation, id responseObject))success
    failure:(void (^)(AFHTTPRequestOperation *operation, NSError *error)) failure {
    [[MyApiClient sharedDeviceServiceInstance] getPath:[NSString stringWithFormat:@"%@", netPath]
      parameters:nil success:success  failure:failure];
}

However, I need to process the json object data returned from getPath before returning to getDevices().
I’ve tried this:

- (void)getDevices:(NSString *)netPath success:(void (^)(id  myResults))success
        failure:(void (^)(AFHTTPRequestOperation *operation, NSError *error)) failure {

  [[MyApiClient sharedDeviceServiceInstance] getPath:[NSString stringWithFormat:@"%@", netPath]
    parameters:nil
    success:^(AFHTTPRequestOperation *operation, id responseObject)
   {
     ... can process json object here ...
   }                           
   failure:^(AFHTTPRequestOperation *operation, NSError *error) {
     ... process errors here ...
   }];
}

But now there is no call back to getDevices().
So how do I process the json object in getDevices & have the block return on completion?
Appreciate the help, as I’m new to blocks.

Answer 1

That’s really easy to do: Just invoke the block by calling it like a function.

- (void)getDevices:(NSString *)netPath 
           success:(void (^)(id  myResults))success
           failure:(void (^)(AFHTTPRequestOperation *operation, NSError *error)) failure
{
  [[MyApiClient sharedDeviceServiceInstance] 
     getPath:netPath
  parameters:nil
     success:^(AFHTTPRequestOperation *operation, id responseObject)
     {
       id myResults = nil;
       // ... can process json object here ...
       success(myResults);
     }                           
     failure:^(AFHTTPRequestOperation *operation, NSError *error) {
       // ... process errors here ...
       failure(operation, error);
     }];
}

EDIT:

Based on the code you posted I think the following interface would be more clear:

typedef void(^tFailureBlock)(NSError *error);

- (void)getDevicesForUserID:(NSString *)userID 
                    success:(void (^)(NSArray* devices))successBlock
                    failure:(tFailureBlock)failureBlock;