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- #ifndef dispatch_cancellable_block_h
- #define dispatch_cancellable_block_h
- #import <Foundation/Foundation.h>
- typedef void(^dispatch_cancelable_block_t)(BOOL cancel);
- NS_INLINE dispatch_cancelable_block_t dispatch_after_delay(NSTimeInterval delay, dispatch_block_t block) {
- if (block == nil) {
- return nil;
- }
- // First we have to create a new dispatch_cancelable_block_t and we also need to copy the block given (if you want more explanations about the __block storage type, read this: https://developer.apple.com/library/ios/documentation/cocoa/conceptual/Blocks/Articles/bxVariables.html#//apple_ref/doc/uid/TP40007502-CH6-SW6
- __block dispatch_cancelable_block_t cancelableBlock = nil;
- __block dispatch_block_t originalBlock = [block copy];
- // This block will be executed in NOW() + delay
- dispatch_cancelable_block_t delayBlock = ^(BOOL cancel){
- if (cancel == NO && originalBlock) {
- originalBlock();
- }
- // We don't want to hold any objects in the memory
- originalBlock = nil;
- };
- cancelableBlock = [delayBlock copy];
- dispatch_after(dispatch_time(DISPATCH_TIME_NOW, delay * NSEC_PER_SEC), dispatch_get_main_queue(), ^{
- // We are now in the future (NOW() + delay). It means the block hasn't been canceled so we can execute it
- if (cancelableBlock) {
- cancelableBlock(NO);
- cancelableBlock = nil;
- }
- });
- return cancelableBlock;
- }
- NS_INLINE void cancel_block(dispatch_cancelable_block_t block) {
- if (block == nil) {
- return;
- }
- block(YES);
- block = nil;
- }
- #endif /* dispatch_cancellable_block_h */
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