实现短信倒计时

@implementation ForgetViewController {

__strong NSTimer * timer;

NSInteger          secondes;

}

- (void)dealloc{

if(timer != nil){

[timer invalidate];

timer = nil;

}

}

- (void)btnClick:(UIButton *)sender {

secondes= 59;

if (!timer) {

timer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(timerFired:) userInfo:nil repeats:YES];

[[NSRunLoop currentRunLoop] addTimer:timer forMode:NSRunLoopCommonModes];

[timer fire];

}

-(void)timerFired:(id) sender

{

if(secondes <=0) {

self.codeBtn.enabled = YES;

[self.codeBtn setTitle:@"重新获取" forState:UIControlStateNormal];

} else {

NSString * title = [NSString stringWithFormat:@"(%lds)后重发", secondes];

[self.codeBtn setTitle:title forState:UIControlStateNormal];

}

secondes--;

}