記錄我工作中使用到的GCD方法店量，定期更新完善。
Grand Central Dispatch (GCD) 是Apple開(kāi)發(fā)的一個(gè)多核編程的較新的解決方法以舒。
- GCD可用于多核的并行運(yùn)算
- GCD會(huì)自動(dòng)利用更多的CPU內(nèi)核（比如雙核钾菊、四核）
- GCD會(huì)自動(dòng)管理線程的生命周期（創(chuàng)建線程辑畦、調(diào)度任務(wù)、銷(xiāo)毀線程）
程序員只需要告訴GCD想要執(zhí)行什么任務(wù)布朦，不需要編寫(xiě)任何線程管理代碼囤萤。但是看了很多文章，感覺(jué)GCD太大了是趴，根本就記不住阁将，所以寫(xiě)下這個(gè)筆記，記錄下自己使用到的方法右遭。
- 同時(shí)執(zhí)行多個(gè)異步操作做盅，都執(zhí)行完畢，再執(zhí)行某個(gè)方法窘哈。
// 創(chuàng)建信號(hào)量
_semaphore = dispatch_semaphore_create(0);
// 創(chuàng)建全局并行
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
dispatch_group_t group = dispatch_group_create();
dispatch_group_async(group, queue, ^{
// 請(qǐng)求一
//獲取輪播圖數(shù)據(jù)
[self getCarouselData];
});
dispatch_group_async(group, queue, ^{
// 請(qǐng)求二
//獲取首頁(yè) 3 和 8 張圖
[self getTemplateImg];
});
dispatch_group_notify(group, queue, ^{
// 2個(gè)請(qǐng)求對(duì)應(yīng)2次信號(hào)等待
dispatch_semaphore_wait(_semaphore, DISPATCH_TIME_FOREVER);
dispatch_semaphore_wait(_semaphore, DISPATCH_TIME_FOREVER);
//回到主線程刷新ui
dispatch_async(dispatch_get_main_queue(), ^{
DLog(@"------------ 請(qǐng)求完畢 ---------------");
[self.tableView reloadData];
[self.tableView.mj_header endRefreshing];
});
});
在請(qǐng)求方法獲取到數(shù)據(jù)時(shí)
//[self getCarouselData];
DLog(@"------------ 第一次 請(qǐng)求完畢 ---------------");
dispatch_semaphore_signal(_semaphore);
- GCD進(jìn)行延遲操作
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(1.0f * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
[self.navigationController popViewControllerAnimated:YES];
});
- GCD倒計(jì)時(shí)
__block int timeout= 59; //倒計(jì)時(shí)時(shí)間
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); //每秒執(zhí)行
dispatch_source_set_event_handler(_timer, ^{
if(timeout<=0){ //倒計(jì)時(shí)結(jié)束吹榴，關(guān)閉
dispatch_source_cancel(_timer);
dispatch_async(dispatch_get_main_queue(), ^{
//設(shè)置界面的按鈕顯示 根據(jù)自己需求設(shè)置
[self.getCode setTitle:@"獲取驗(yàn)證碼" forState:UIControlStateNormal];
self.getCode.userInteractionEnabled = YES;
});
}else{
// int minutes = timeout / 60;
int seconds = timeout % 120;
NSString *strTime = [NSString stringWithFormat:@"%.2d", seconds];
dispatch_async(dispatch_get_main_queue(), ^{
//設(shè)置界面的按鈕顯示 根據(jù)自己需求設(shè)置
[self.getCode setTitle:[NSString stringWithFormat:@"%@秒后重獲",strTime] forState:UIControlStateNormal];
self.getCode.userInteractionEnabled = NO;
});
timeout--;
}
});
dispatch_resume(_timer);
4.異步操作，主線程刷新UI
dispatch_async(dispatch_get_global_queue(0, 0), ^{
//通知主線程刷新
dispatch_async(dispatch_get_main_queue(), ^{
//回調(diào)或者說(shuō)是通知主線程刷新滚婉，
[self.mTableView reloadData];;
});
});
5.調(diào)度組
//1.創(chuàng)建調(diào)度組
dispatch_group_t group = dispatch_group_create();
//2.隊(duì)列
dispatch_queue_t q = dispatch_get_global_queue(0, 0);
//3.調(diào)度組監(jiān)聽(tīng)隊(duì)列
dispatch_group_enter(group);
dispatch_group_async(group, q, ^{
sleep(1);
NSLog(@"download 1");
dispatch_group_leave(group);
});
dispatch_group_enter(group);
dispatch_group_async(group, q, ^{
NSLog(@"download 2");
dispatch_group_leave(group);
});
dispatch_group_notify(group, q, ^{
NSLog(@"完成");
});
