第一步：定义一个开始时间（如果需要改变按钮上的显示以及关闭按钮的功能，可在这里设置）
__block int takeTime = 60;
（
self.timeButton.enabled = NO;
[self.timeButton setTitleColor:DTCE_COLOR forState:UIControlStateNormal];
self.timeButton.layer.borderColor = DTCE_COLOR.CGColor;
[self.timeButton setTitle:[NSString stringWithFormat:@"%i秒",takeTime] forState:UIControlStateNormal];
）
第二步：设置按钮标题变为数字倒计时
[self.timeButton setTitle:[NSString stringWithFormat:@"%i秒",takeTime] forState:UIControlStateNormal];
第三步：开始时间倒计时
[NSTimer scheduledTimerWithTimeInterval:1 repeats:YES block:^(NSTimer * _Nonnull timer) {
//当倒计时为0时（恢复按钮的显示和功能，销毁计时器。这里记得一定要return下，不然会到-1.）
if(takeTime ==0) {
（
self.timeButton.enabled=YES;
[self.timeButton setTitleColor:MW_GrassGreenColor forState:UIControlStateNormal];
self.timeButton.layer.borderColor=MW_GrassGreenColor.CGColor;
[self.timeButtonsetTitle:@"获取验证码"forState:UIControlStateNormal];
）
[timerinvalidate];//销毁计时器
return;
}
takeTime --;
[self.timeButton setTitle:[NSString stringWithFormat:@"%i秒",takeTime] forState:UIControlStateNormal];
}];
