浅谈iOS开发中方法延迟执行的几种方式

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

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文／笨笨编程（简书作者）
原文链接：http://www.jianshu.com/p/6ed28a29b391
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