iOS之实现倒计时功能

倒计时在发送验证码是常见的功能，怎么实现这个功能。正所谓会者不难，难者不会。在此遍博客来实现一下。具体代码可以参考 倒计时Demo

一、实现思路

倒计时功能的实现：

• 当触发倒计时的button时，才进行倒计时功能

• 倒计时完毕时，使button可用即可以再次点击来重新发送

二、具体代码的实现

EDCountdown.h

////  EDCountdown.h//  Countdown////  Created by humor on 15/12/31.//  Copyright © 2015年 onefiter. All rights reserved.//#import <Foundation/Foundation.h>@class EDCountdown;@protocol EDCountdownDelegate <NSObject>/** *  周期性的通知外界，自创建计时器到当前时间差值 * *  @param sender     计时器 *  @param timeOffset 自创建计时器到当前时间差值 */- (void)notifyCountTimeCallBack:(id)sender withTimeOffset:(NSTimeInterval)timeOffset;@end@interface EDCountdown : NSObject@property(nonatomic, weak  )   id<EDCountdownDelegate> delegate;@property(nonatomic, assign)   BOOL isOpen;@property(nonatomic, assign)   NSTimeInterval timeInterval;- (void)handleCountTimerEvent:(id)sender;@end

EDCountdown.m

////  EDCountdown.m//  Countdown////  Created by humor on 15/12/31.//  Copyright © 2015年 onefiter. All rights reserved.//#import "EDCountdown.h"@interface EDCountdown ()@property (nonatomic, strong) NSTimer *timer;@property (nonatomic, assign) NSTimeInterval startTime;@end@implementation EDCountdown- (instancetype)init{    if (self = [super init]) {        _timeInterval = 1;    }    return self;}- (void)dealloc{    self.isOpen = NO;}- (void)setIsOpen:(BOOL)isOpen{    _isOpen = isOpen;    __block dispatch_block_t mainBlock = NULL;    if (_isOpen) {        mainBlock = ^{            if (_timer.isValid) {                [_timer invalidate];            }                _timer = [NSTimer scheduledTimerWithTimeInterval:_timeInterval target:self selector:@selector(handleCountTimerEvent:) userInfo:nil repeats:YES];                _startTime = CFAbsoluteTimeGetCurrent();        };    }    else    {        mainBlock = ^{            if (_timer.isValid) {                [_timer invalidate];            }            _timer = nil;        };    }    if ([NSThread isMainThread]) {        mainBlock();    }    else    {        dispatch_async(dispatch_get_main_queue(), mainBlock);    }}- (void)handleCountTimerEvent:(id)sender{    if ([_delegate respondsToSelector:@selector(notifyCountTimeCallBack:withTimeOffset:)]) {        NSTimeInterval  deltaTime = CFAbsoluteTimeGetCurrent() - _startTime;        [_delegate notifyCountTimeCallBack:self withTimeOffset:deltaTime];    }}@end