Block references as instance vars in Objective-C
I was wondering if it's possible to store a reference to an anonymous function (block) as an instance variable in Objective-C.
I know how to use delegation, target-action, etc. I am not talking about this.
Sure.
typedef void(^MyCustomBlockType)(void);
@interface MyCustomObject {
MyCustomBlockType block;
}
@property (nonatomic, copy) MyCustomBlockType block; //note: this has to be copy, not retain
- (void) executeBlock;
@end
@implementation MyCustomObject
@synthesize block;
- (void) executeBlock {
if (block != nil) {
block();
}
}
- (void) dealloc {
[block release];
[super dealloc];
}
@end
//elsewhere:
MyCustomObject * object = [[MyCustomObject alloc] init];
[object setBlock:^{
NSLog(@"hello, world!");
}];
[object executeBlock];
[object release];
Yes, you most certainly can store a reference to a (copy) of an Objective-C block. The variable declaration is a little bit hairy, like C function pointers, but beyond that it's no problem. For a block that takes and id
and returns void:
typedef void (^MyActionBlockType)(id);
@interface MyClass : NSObject
{
}
@property (readwrite,nonatomic,copy) MyActionBlockType myActionBlock;
@end
will do the trick.