How to store blocks in properties in Objective-C?

Edit: updated for ARC

typedef void(^MyCustomBlock)(void);

@interface MyClass : NSObject

@property (nonatomic, copy) MyCustomBlock customBlock;

@end

@implementation MyClass

@end

MyClass * c = [[MyClass alloc] init];
c.customBlock = ^{
  NSLog(@"hello.....");
}

c.customBlock();

Alternatively, without the typedef

@property (copy, nonatomic) void (^selectionHandler) (NSDictionary*) ;

You can find a very good explanation of this in WWDC 2012 session 712 starting in page 83. The correct way of saving a block under ARC is the following:

@property(strong) my_block_type work;

Be careful with the retain cycles. A good way to solve is set the block to nil when you do not need it anymore:

self.work = nil;