浅谈iOS开发中方法延迟执行的几种方式

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Method1. performSelector方法

Method2. NSTimer定时器

Method3. NSThread线程的sleep

Method4. GCD

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公用延迟执行方法

- (void)delayMethod{
    NSLog(@"delayMethodEnd");
}

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Method1:performSelector

[self performSelector:@selector(delayMethod) withObject:nil/*可传任意类型参数*/ afterDelay:2.0];
注：此方法是一种非阻塞的执行方式，未找到取消执行的方法。

程序运行结束
2015-08-31 10:56:59.361 CJDelayMethod[1080:39604] delayMethodStart 2015-08-31 10:56:59.363 CJDelayMethod[1080:39604] nextMethod 2015-08-31 10:57:01.364 CJDelayMethod[1080:39604] delayMethodEnd

Method2:NSTimer定时器

NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:2.0 target:self selector:@selector(delayMethod) userInfo:nil repeats:NO];
注：此方法是一种非阻塞的执行方式，
取消执行方法：- (void)invalidate;即可

程序运行结束
2015-08-31 10:58:10.182 CJDelayMethod[1129:41106] delayMethodStart 2015-08-31 10:58:10.183 CJDelayMethod[1129:41106] nextMethod 2015-08-31 10:58:12.185 CJDelayMethod[1129:41106] delayMethodEnd

Method3:NSThread线程的sleep

[NSThread sleepForTimeInterval:2.0];
注：此方法是一种阻塞执行方式，建议放在子线程中执行，否则会卡住界面。但有时还是需要阻塞执行，如进入欢迎界面需要沉睡3秒才进入主界面时。
没有找到取消执行方式。

程序运行结束
2015-08-31 10:58:41.501 CJDelayMethod[1153:41698] delayMethodStart 2015-08-31 10:58:43.507 CJDelayMethod[1153:41698] nextMethod

Method4:GCD

__block ViewController/*主控制器*/ *weakSelf = self;

dispatch_time_t delayTime = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2.0/*延迟执行时间*/ * NSEC_PER_SEC));

dispatch_after(delayTime, dispatch_get_main_queue(), ^{
    [weakSelf delayMethod];
});`

注：此方法可以在参数中选择执行的线程，是一种非阻塞执行方式。没有找到取消执行方式。

程序运行结束
2015-08-31 10:59:21.652 CJDelayMethod[1181:42438] delayMethodStart 2015-08-31 10:59:21.653 CJDelayMethod[1181:42438] nextMethod 2015-08-31 10:59:23.653 CJDelayMethod[1181:42438] delayMethodEnd

完整代码参见：

//
// ViewController.m
// CJDelayMethod
//
// Created by 陈杰 on 8/31/15.
// Copyright (c) 2015 chenjie. All rights reserved.
//

#import "ViewController.h"
@interface ViewController ()
@property (nonatomic, strong) NSTimer *timer;
@end
@implementation ViewController
- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    NSLog(@"delayMethodStart");
    [self methodOnePerformSelector];
//    [self methodTwoNSTimer];
//    [self methodThreeSleep];
//    [self methodFourGCD];
    NSLog(@"nextMethod");
}
- (void)methodFiveAnimation{
    [UIView animateWithDuration:0 delay:2.0 options:UIViewAnimationOptionAllowUserInteraction animations:^{        
    } completion:^(BOOL finished) {
        [self delayMethod];
    }];
}
- (void)methodFourGCD{
    __block ViewController` *`weakSelf = self;
    dispatch_time_t delayTime = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2.0 * NSEC_PER_SEC));
    dispatch_after(delayTime, dispatch_get_main_queue(), ^{
        [weakSelf delayMethod];
    });
}
- (void)methodThreeSleep{
    [NSThread sleepForTimeInterval:2.0];
}
- (void)methodTwoNSTimer{
    NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:2.0 target:self selector:@selector(delayMethod) userInfo:nil repeats:NO];
}
- (void)methodOnePerformSelector{
    [self performSelector:@selector(delayMethod) withObject:nil/*可传任意类型参数*/ afterDelay:2.0];
}
- (void)delayMethod{
    NSLog(@"delayMethodEnd");
}
- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}
@end