How to write an Objective-C Completion Block

Question

I\'m in a situation where need to call a class method from my view controller, have it do it\'s thing, but then perform some actions ONLY AFTER the class method has complete

Answer 1

I wrote a completionBlock for a class which will return the values of a dice after they have been shaked:

1. Define typedef with returnType (.h above @interface declaration)

   typedef void (^CompleteDiceRolling)(NSInteger diceValue);
   

2. Define a @property for the block (.h)

   @property (copy, nonatomic) CompleteDiceRolling completeDiceRolling;
   

3. Define a method with finishBlock (.h)

   - (void)getDiceValueAfterSpin:(void (^)(NSInteger diceValue))finishBlock;
   

4. Insert previous defined method in .m file and commit finishBlock to @property defined before

   - (void)getDiceValueAfterSpin:(void (^)(NSInteger diceValue))finishBlock{
       self.completeDiceRolling = finishBlock;
   }
   

5. To trigger completionBlock pass predefined variableType to it (Don't forget to check whether the completionBlock exists)

   if( self.completeDiceRolling ){
       self.completeDiceRolling(self.dieValue);
   }