Block recursion and breaking retain cycle

Question

To better illustrate the question, consider the following simplified form of block recursion:

__block void (^next)(int) = ^(int index) {
    if (index == 3) {
           


        

Answer 1

I think @newacct is correct about @Matt Wilding's solution; it does seem that nothing will have a strong ref to the next block in that case and will result in a run time exception when run (at least it did for me).

I don't know how common it is to find recursively called blocks in the wild in objc. However, in a real world implementation (if actually required) on say, a view controller, one might define the block and then set up an internal interface property with a strong reference to said block:

typedef void(^PushButtonBlock)();

@interface ViewController ()
@property (strong, nonatomic) PushButtonBlock pushButton;
@end

@implementation ViewController
  ... 
  // (in viewDidLoad or some such)
  __weak ViewController *weakSelf = self;

  self.pushButton = ^() {
    [weakSelf.button pushIt];
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), weakSelf.pushButton);
  };

  self.pushButton();
  ...
@end

This runs fine for me and has no compiler warnings about retain cycles (and no leaks in instruments). But, I think I would probably steer clear of doing this (recursive block calls) in most cases in objc - it's smelly. But interesting in any case.