How Do I Declare A Block in Objective-C? source : http://fuckingblocksyntax.com

block-syntax

// As a local variable.
returnType (^blockName)(parameterTypes) = ^returnType(parameters) {...};

// As a property.
@property (nonatomic, copy) returnType (^blockName)(parameterTypes);

// As a method parameter.
- (void)someMethodThatTakesABlock:(returnType (^)(parameterTypes))blockName {...}

// As an argument to a method call.
[someObject someMethodThatTakesABlock: ^returnType (parameters) {...}];

// As a typedef.
typedef returnType (^TypeName)(parameterTypes);
TypeName blockName = ^returnType(parameters) {...};