Ios 如何处理：有五个api请求并行运行，第二个请求依赖于第四个请求'；s的反应

我遇到了一个问题，我想知道更好的解决方法

有五个api请求并行运行，第二个请求依赖于第四个请求的响应，但所有5个请求都已在运行。更好的方法是什么

我需要建议。提前感谢。

考虑gcd：

 dispatch_group_t group = dispatch_group_create();
 dispatch_group_async(group, dispatch_get_global_queue(0,0), ^{
     // operation 1
 });
 dispatch_group_async(group, dispatch_get_global_queue(0,0), ^{
     // operation 2
 });
 dispatch_group_notify(group, dispatch_get_global_queue(0,0), ^{
     // finish
});

以gcd为例：

 dispatch_group_t group = dispatch_group_create();
 dispatch_group_async(group, dispatch_get_global_queue(0,0), ^{
     // operation 1
 });
 dispatch_group_async(group, dispatch_get_global_queue(0,0), ^{
     // operation 2
 });
 dispatch_group_notify(group, dispatch_get_global_queue(0,0), ^{
     // finish
});

---

地面工作正常

//create a dispatch group
dispatch_group_t serviceGroup = dispatch_group_create();

//request 1
dispatch_group_async(serviceGroup,queue,^{
    // some work here
});

//request 3
dispatch_group_async(serviceGroup,queue,^{
    // some work here
});

//request 5
dispatch_group_async(serviceGroup,queue,^{
    // some work here
});

//request 4
dispatch_group_enter(serviceGroup);
[something startWithCompletion:^() {
    //result
    dispatch_group_leave(serviceGroup);
    //request 2
}];

---

地面工作正常

//create a dispatch group
dispatch_group_t serviceGroup = dispatch_group_create();

//request 1
dispatch_group_async(serviceGroup,queue,^{
    // some work here
});

//request 3
dispatch_group_async(serviceGroup,queue,^{
    // some work here
});

//request 5
dispatch_group_async(serviceGroup,queue,^{
    // some work here
});

//request 4
dispatch_group_enter(serviceGroup);
[something startWithCompletion:^() {
    //result
    dispatch_group_leave(serviceGroup);
    //request 2
}];

---

谢谢你的建议@lee Jabez谢谢你的建议@lee Jabez谢谢你的建议@Ronant谢谢你的建议@ronan