变更记录

方案名称

时间 - 倒计时器的实现

关键字

时间 \ 倒计时 \ 计时器 \ 延时执行

需求场景

1. 倒计时
2. 延时执行

参考链接

1. GitHub - TTGCDTimerWrapper

详细内容

1. 方法定义（注：对 TTGCDTimerWrapper 源代码做了少许修改）

TTGCDTimerWrapper.h

#import <Foundation/Foundation.h>

@interface TTGCDTimerWrapper : NSObject

//Either a dispatch queue is provided or a default dispatch queue
//will be used. (dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);)
- (id)initWithTargetQueue:(dispatch_queue_t)targetQueue;

//Will perform a block on the provided queue (or default queue) after a given interval.
//One can also set it to repeat.
- (void)afterInterval:(NSTimeInterval)interval perform:(void (^)())block repeats:(BOOL) repeats;

//Will cancel the timer and if needed the targetQueue is released.
- (void)cancel;

@end

TTGCDTimerWrapper.m

#import "TTGCDTimerWrapper.h"

@implementation TTGCDTimerWrapper {
    dispatch_queue_t _queue;
    dispatch_source_t _timer;
}

- (id)initWithTargetQueue:(dispatch_queue_t)targetQueue {
    self = [super init];

    if(self) {
        _queue = targetQueue ?:dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
        _timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, _queue);
    }
    return self;
}

- (void) afterInterval: (NSTimeInterval)interval perform:(void (^)())block repeats:(BOOL) repeats {
    [self performSync: ^{

        NSTimeInterval timeIntervalInNSec = interval * NSEC_PER_SEC;

        dispatch_source_set_timer(_timer, dispatch_time(DISPATCH_TIME_NOW, timeIntervalInNSec), timeIntervalInNSec, 0);

        dispatch_source_set_event_handler(_timer, ^{
            if(block){
                block();
            }
            if (!repeats) {
                [self cancel];
            }
        });

        dispatch_resume(_timer);
    }];
}

- (void)performSync: (dispatch_block_t)block {
    dispatch_sync(_queue, block);
}

- (void)cancel {
    [self performSync: ^{
        if(_timer) {
            dispatch_source_cancel(_timer);

#if __IPHONE_OS_VERSION_MIN_REQUIRED < 60000
            dispatch_release(_timer);
#endif
            _timer = NULL;
        }
    }];
}

- (void)dealloc {
    [self cancel];
    _queue = NULL;
}

@end

2. 示例

• 注意点 1 ：一定要声明为成员变量
• 注意点 2 ：无论是否 ARC, 一定要在 dealloc 中执行 cancel 方法

//
//  ViewController.m
//  testproject
//
//  Created by viktyz on 16/1/10.
//  Copyright © 2016年 Alfred Jiang. All rights reserved.
//

#import "ViewController.h"
#import "TTGCDTimerWrapper.h"

@interface ViewController ()
{
    TTGCDTimerWrapper *timer;   //注意点 1 ：一定要声明为成员变量
}

@end

@implementation ViewController

- (void)dealloc
{
    [timer cancel]; //注意点 2 ：无论是否 ARC, 一定要在 dealloc 中执行 cancel 方法
}

- (void)viewDidLoad
{
    [super viewDidLoad];

    timer = [[TTGCDTimerWrapper alloc] initWithTargetQueue:nil];

    [timer afterInterval:5.0
                 perform:^{
                    NSLog(@"After 5 Seconds");
                 }
                 repeats:YES];
}


- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end

效果图

（无）

备注

• 注意点 1 ：一定要声明为成员变量

• 注意点 2 ：无论是否 ARC, 一定要在 dealloc 中执行 cancel 方法

• 时间 - 延时执行解决方案