ios - 如何在同一个函数中只有 1 个完成处理程序用于 2 个 Alamofire 请求

Question

我有一个函数，里面有 2 个 Alamofire 请求和一个完成处理程序。一旦我的两个请求都完成了从服务器下载数据，我想重新加载我的 collectionView。我在函数中有一个完成处理程序，但它被调用了两次，这导致我的 collectionView 重新加载两次，我只想重新加载一次。有什么办法可以做到吗？非常感谢!

func getFeedVideos(completion: @escaping (_ completedDownloadVideo: Bool) -> ()){

    Alamofire.request(youTubeUrl, method: .get, parameters: ["part":"snippet","maxResults": "20","nextPageToken" : "pageToken", "playlistId": playListId, "key": googleAPIKey], encoding: URLEncoding.default, headers: nil).responseJSON { (response) in
        guard let data = response.data else {return}
        do {
            let json = try JSONDecoder().decode(serverData.self, from: data)
            self.dataFromAPI = json.items
            completion(true)
        } catch let jsonErr{
            print(jsonErr)
        }
    }

    Alamofire.request(youTubeChannelUrl, method: .get, parameters: ["part":"snippet", "key": googleAPIKey, "id": youTubeChannelId], encoding: URLEncoding.default, headers: nil).responseJSON { (response) in
        guard let data = response.data else {return}
        do {
            let json = try JSONDecoder().decode(channelInfo.self, from: data)
            self.channelData = json.items
            completion(true)
        } catch let jsonErr{
            print(jsonErr)
        }
    }
}

这是我在 ViewDidLoad 中调用函数的方式

    override func viewDidLoad() {
    super.viewDidLoad()
    getFeedVideos { (complete) in
        if complete{
            DispatchQueue.main.async {
                self.collectionView?.reloadData()
            }
        }
    }
}

Answer 1

更好的解决方案

使用 DispatchGroup 下面是例子

   let dispatchGroup = DispatchGroup()

    dispatchGroup.enter()

Alamofire.request(youTubeUrl, method: .get, parameters: ["part":"snippet","maxResults": "20","nextPageToken" : "pageToken", "playlistId": playListId, "key": googleAPIKey], encoding: URLEncoding.default, headers: nil).responseJSON { (response) in
        guard let data = response.data else {return}
        do {
            let json = try JSONDecoder().decode(serverData.self, from: data)
            self.dataFromAPI = json.items
            completion(true)
        } catch let jsonErr{
            print(jsonErr)
        }
      dispatchGroup.leave()
    }

 dispatchGroup.enter()

    Alamofire.request(youTubeChannelUrl, method: .get, parameters: ["part":"snippet", "key": googleAPIKey, "id": youTubeChannelId], encoding: URLEncoding.default, headers: nil).responseJSON { (response) in
        guard let data = response.data else {return}
        do {
            let json = try JSONDecoder().decode(channelInfo.self, from: data)
            self.channelData = json.items
            completion(true)
        } catch let jsonErr{
            print(jsonErr)
        }
       dispatchGroup.leave()
    }

这是魔法线

dispatchGroup.notify(queue: .main) {
    print("Both functions complete 👍")
}

Each call to enter() must be matched later on with a call to leave(), after which the group will call the closure provided to notify().