原文來自pianzhidenanren的AFNetworking+GCD處理并發(fā)問題

我們?cè)诰幊痰臅r(shí)候會(huì)經(jīng)常會(huì)出現(xiàn)這樣的需求：同時(shí)請(qǐng)求幾個(gè)接口回調(diào)成功以后在統(tǒng)一刷新UI坦仍，解決這個(gè)問題的方法有很多今天我們就說明下GCD下解決的方式坞古。

GCD的leave和enter

我們利用dispatch_group_t創(chuàng)建隊(duì)列組，手動(dòng)管理group關(guān)聯(lián)的block運(yùn)行狀態(tài)，進(jìn)入和退出group的次數(shù)必須匹配

//1.創(chuàng)建隊(duì)列組
    dispatch_group_t group = dispatch_group_create();
    //2.創(chuàng)建隊(duì)列
    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
    //3.添加請(qǐng)求
    dispatch_group_async(group, queue, ^{
        dispatch_group_enter(group);
        [HomeRequest getPointBuyAllConfigurationStrategyType:_dataType success:^(NSInteger code, NSDictionary *dict) {
            dispatch_group_leave(group);
        } failuer:^(NSInteger code, NSString *message) {
            dispatch_group_leave(group);
        }];
    });
    dispatch_group_async(group, queue, ^{
        dispatch_group_enter(group);
        [HomeRequest getStockLeverRiskStockCode:_buyingStrategyModel.stockCode strategyType:_dataType success:^(NSInteger code, NSDictionary *dict) {
            dispatch_group_leave(group);
        } failuer:^(NSInteger code, NSString *message) {
            dispatch_group_leave(group);
        }];
    });
    //4.隊(duì)列組所有請(qǐng)求完成回調(diào)刷新UI
    dispatch_group_notify(group, dispatch_get_main_queue(), ^{
        NSLog(@"model:%f",_buyingStrategyModel.leverrisk);
    });

GCD的信號(hào)量dispatch_semaphore_t

這種方式有點(diǎn)類似于通知模式陨帆，是利用監(jiān)聽信號(hào)量來發(fā)送消息以達(dá)到并發(fā)處理的效果，我們來看看代碼：

//創(chuàng)建信號(hào)量  
    dispatch_semaphore_t semaphore = dispatch_semaphore_create(0);  
      
    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, ^{  
        [HomeRequest getPointBuyAllConfigurationStrategyType:_dataType success:^(NSInteger code, NSDictionary *dict) {  
            dispatch_semaphore_signal(semaphore);  
        } failuer:^(NSInteger code, NSString *message) {  
            dispatch_semaphore_signal(semaphore);  
        }];  
    });  
    dispatch_group_async(group, queue, ^{  
        [HomeRequest getStockLeverRiskStockCode:_buyingStrategyModel.stockCode strategyType:_dataType success:^(NSInteger code, NSDictionary *dict) {  
            dispatch_semaphore_signal(semaphore);  
        } failuer:^(NSInteger code, NSString *message) {  
            dispatch_semaphore_signal(semaphore);  
        }];  
    });  
    dispatch_group_notify(group, queue, ^{  
        dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);  
        dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);  
        NSLog(@"信號(hào)量為0");  
    });  

這兩種方式都可以達(dá)到并發(fā)處理的效果，當(dāng)然還有其他方式怎披，大家一起學(xué)習(xí)吧！