知道使用异步方法对数组的迭代何时完成

问题描述

假设我有一个字符串数组，我调用了一个从它返回一个 int 的异步方法.我想知道我的 int 数组中何时有这些 int 值.

Lets say i have an array of strings, and i call an async method that returns an int from it. I want to know when i have those int values in my array of ints.

let rndStrings = ["a", "b", "c"]
var rndInts = [Int]()
rndStrings.forEach { rndString in 
   someAsyncMethod { intResult in
     rndInts.append(intResult)
   }
}

我想等到 rndInts 拥有所有 3 个值

I want to wait until rndInts has all 3 values

推荐答案

不要等待.通过 DispatchGroup 获得通知.

let rndStrings = ["a", "b", "c"]
let group = DispatchGroup()
var rndInts = [Int]()
rndStrings.forEach { rndString in 
   group.enter()
   someAsyncMethod { intResult in
     rndInts.append(intResult)
     group.leave()
   }
}
group.notify(queue: DispatchQueue.main) {
   print("finished")
}

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