GCD实现倒计时
__blockint timeout=59;//倒计时时间
dispatch_queue_t queue =dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT,0);
dispatch_source_t _timer =dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER,0,0,queue);
dispatch_source_set_timer(_timer,dispatch_walltime(NULL,0),1.0*NSEC_PER_SEC,0);//每秒执行
dispatch_source_set_event_handler(_timer, ^{
if(timeout<=0){//倒计时结束,关闭
dispatch_source_cancel(_timer);
dispatch_async(dispatch_get_main_queue(), ^{
//设置界面显示 根据自己需求设置
});
}else{
int seconds = timeout %60;
NSString *strTime = [NSStringstringWithFormat:@"%.2d", seconds];
dispatch_async(dispatch_get_main_queue(), ^{
//设置界面显示 根据自己需求设置
});
timeout--;
}
});
dispatch_resume(_timer);
// 提供单例接口
+ (instancetype) sharedInstantObj;
#pragma mark - 重写allocWithZone, alloc方法最终会调用allocWithZone
+ (instancetype)allocWithZone:(struct_NSZone *)zone{
staticinstantObj* obj;
staticdispatch_once_t onceToken;
//dispatch_once可以保证block中的代码永远只被执行一次
dispatch_once(&onceToken, ^{
obj = [super allocWithZone:zone];
});
return obj;
}
+ (instancetype)sharedInstantObj{
return [[self alloc] init];
}
GCD实现开启并发线程
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND,0), ^{
//设置界面显示 根据自己需求设置
});
dispatch_async(dispatch_get_main_queue(), ^{
//设置界面显示 根据自己需求设置
});
GCD队列暂停执行处理
// 挂起队列
dispatch_suspend(queue);
// 恢复队列执行
dispatch_resume(queue);