ios嵌套的异步并行任务场景

标签：dispatch_group   嵌套   异步   并行任务   

场景1：

从数据源读到N个值，然后需要遍历这N个值，分别发起http请求。处理完成之后，调用一个最终汇总的方法

这个场景如果用js的async框架，很容易就能实现：

async.series([task1, task2, task3], function(err){
    // 汇总代码
});

function task1(callback){
    // http请求
    callback(null);
}

function task2(callback){
    // http请求
    callback(null);
}

function task3(callback){
    // http请求
    callback(null);
}

dispatch_group_t group = dispatch_group_create();
            
while([rs next]){
                
    dispatch_group_enter(group);
               
    [syncService refreshMembersWithEnterpriseId:enterpriseId LatestSyncTime:latestSyncDate Block:^(BOOL flag){
        dispatch_group_leave(group);
    }];
}        

dispatch_group_notify(group, dispatch_get_main_queue(), ^{
    // 汇总代码
});

后来需求变化了，场景更复杂了点。针对每个值，都要发起多个http请求（场景1只需要请求1次）。所有请求都结束以后，再调用汇总方法

所以一开始我写成类似这样：

dispatch_group_t group = dispatch_group_create();
            
while([rs next]){
                
    dispatch_group_enter(group);
    
    dispatch_group_t group_inner = dispatch_group_create();
                
    dispatch_group_enter(group_inner);
    [syncService refreshMembersWithEnterpriseId:enterpriseId LatestSyncTime:latestSyncDate Block:^(BOOL flag){
        dispatch_group_leave(group_inner);
    }];
                
    dispatch_group_enter(group_inner);
    [syncService refreshReportsWithEnterpriseId:enterpriseId LatestSyncTime:latestSyncDate Block:^(BOOL flag){
        dispatch_group_leave(group_inner);
    }];
                
    dispatch_group_notify(group_inner, dispatch_get_global_queue(0, 0), ^{
        dispatch_group_leave(group);
    });
}
            
dispatch_group_notify(group, dispatch_get_main_queue(), ^{
    // 汇总代码
});

dispatch_group_t group = dispatch_group_create();
            
while([rs next]){
                                
    dispatch_group_enter(group);
    [syncService refreshMembersWithEnterpriseId:enterpriseId LatestSyncTime:contactLatestSync Block:^(BOOL flag){
        dispatch_group_leave(group);
    }];
                
    dispatch_group_enter(group);
    [syncService refreshReportsWithEnterpriseId:enterpriseId LatestSyncTime:reportLatestSync Block:^(BOOL flag){
        dispatch_group_leave(group);
    }];
}

dispatch_group_notify(group, dispatch_get_main_queue(), ^{
    // 汇总代码
});

ios嵌套的异步并行任务场景,布布扣,bubuko.com

ios嵌套的异步并行任务场景

标签：dispatch_group   嵌套   异步   并行任务   

原文地址：http://blog.csdn.net/kyfxbl/article/details/34861069