AFNetworking+GCD處理併發問題

我們在編程的時候會經常會出現這樣的需求：同時請求幾個接口回調成功以後在統一刷新UI，解決這個問題的方法有很多今天我們就說明下GCD下解決的方式。

GCD的leave和enter 

我們利用dispatch_group_t創建隊列組，手動管理group關聯的block運行狀態，進入和退出group的次數必須匹配。

//1.創建隊列組
    dispatch_group_t group = dispatch_group_create();
    //2.創建隊列
    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
    //3.添加請求
    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.隊列組所有請求完成回調刷新UI
    dispatch_group_notify(group, dispatch_get_main_queue(), ^{
        NSLog(@"model:%f",_buyingStrategyModel.leverrisk);
    });

GCD的信號量dispatch_semaphore_t

這種方式有點類似於通知模式，是利用監聽信號量來發送消息以達到併發處理的效果，我們來看看代碼：

//創建信號量
    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(@"信號量爲0");
    });

這兩種方式都可以達到併發處理的效果，當然還有其他方式，大家一起學習吧！