block is likely to lead a retain cycle [duplicate]

Answer 1

When you use self within a block, it is captured by the block and could lead to a retain cycle. To cycle occurs when self (or something it has a strong reference to) has a strong reference to the block. To avoid the potential cycle, declare a weak pointer and use that in the block instead:

YourClassName * __weak weakSelf = self;

[_queue addAsynchronousOperationWithBlock:^(block signal) {
    [weakSelf foo:nil];
}];