iOS Ref

Objective-C guide: block syntax

As a local variable

returnType (^blockName)(parameterTypes) = ^returnType(parameters) {...};

As a property

@property (nonatomic, copy, nullability) returnType (^blockName)(parameterTypes);

As a method parameter

- (void)methodThatTakesABlock:(returnType (^nullability)(parameterTypes))blockName;

As an argument to a method call

[someObject methodThatTakesABlock:^returnType (parameters) {...}];

As a `typedef`

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