returnType (^blockName)(parameterTypes) = ^returnType(parameters) {…};
@property (nonatomic, copy) returnType (^blockName)(parameterTypes);
As a method parameter:
(void)methodWithBlock:(returnType (^)(parameterTypes))blockName;
As a typedef:
typedef returnType (^TypeName)(parameterTypes);
TypeName blockName = ^returnType(parameters) {...};