How to simplify callback logic with a Block?

Question

Let\'s say I need to communicate with a class that provides a protocol and calls delegate methods when an operation is complete, as so:

@protocol SomeObjectD         


        

Answer 1

You could do something like this:

typedef void (^AZCallback)(NSError *);

AZCallback callback = ^(NSError *error) {
  if (error == nil) {
    NSLog(@"succeeded!");
  } else {
    NSLog(@"failed: %@", error);
  }
};

SomeObject *o = [[SomeObject alloc] init];
[o setCallback:callback]; // you *MUST* -copy the block
[o doStuff];
...etc;

Then inside SomeObject, you could do:

if ([self hadError]) {
  callback([self error]);
} else {
  callback(nil);
}