我应该如何将 DispatchGroup 用于两个 url 请求？

Question

我正在使用 DispatchGroup 处理两个 url 请求，但没有获得任何数据。我在没有 DispatchGroup 的情况下分别尝试了每种方法，它工作正常。所以问题是我没有正确使用DispatchGroup。请帮忙

    let buildingManager =  BuildingManager()
    let anaManager = AnalyticsManager()
    let group = DispatchGroup()
    let queue = DispatchQueue.global(qos: .background)

    queue.async(group: group) {
        buildingManager.getBuildingInfos(completion: { [weak self] (buildings, success) in
            guard let self = self else {return}

            if success {
                self.buildings = buildings
                print("success")
            } else {
                print("No building infos")
            }
        })
    }

    queue.async(group: group) {
        anaManager.getAnaData(completion: {[weak self] (anaData, success) in
            guard let self = self else {return}

            if success {
                self.analyticsData = anaData
                print("success")
            } else {
                print("No analytics data")
            }
        })
    }

        group.notify(queue: DispatchQueue.main) { [weak self] in
            self?.dataTableView.reloadData()
        }

Answer 1

以前我也遇到过和你一样的问题，我在Swift学到了更多的并行过程。我可能是错的，但在你的位置我会使用 OperationQueue。你可以尝试这样做：

let queue = OperationQueue()

queue.addOperation {
 buildingManager.getBuildingInfos(completion: { [weak self] (buildings, success) in
            guard let self = self else {return}

            if success {
                self.buildings = buildings
                print("success")
            } else {
                print("No building infos")
            }  

            DispatchQueue.main.async {
                self?.dataTableView.reloadData()
            }
        })
}

queue.addOperation {
 anaManager.getAnaData(completion: {[weak self] (anaData, success) in
            guard let self = self else {return}

            if success {
                self.analyticsData = anaData
                print("success")
            } else {
                print("No analytics data")
            }

                DispatchQueue.main.async {
                    self?.dataTableView.reloadData()
                }
        })
}

这与其说是答案，不如说是一种意见。

参考：https://www.raywenderlich.com/5293-operation-and-operationqueue-tutorial-in-swift

Answer 2

我会稍微重构一下，以便根据需要明确地进入和离开您的群组。 queue.async(group:) 的使用仅应在块中的代码尚未异步时使用。

let buildingManager =  BuildingManager()
let anaManager = AnalyticsManager()
let group = DispatchGroup()
let queue = DispatchQueue.global(qos: .background)

queue.async {
    group.enter()
    buildingManager.getBuildingInfos(completion: { [weak self] (buildings, success) in
        defer { group.leave() }

        guard let self = self else {return}

        if success {
            self.buildings = buildings
            print("success")
        } else {
            print("No building infos")
        }
    })

    group.enter()
    anaManager.getAnaData(completion: {[weak self] (anaData, success) in
        defer { group.leave() }

        guard let self = self else {return}

        if success {
            self.analyticsData = anaData
            print("success")
        } else {
            print("No analytics data")
        }
    })

    group.notify(queue: DispatchQueue.main) { [weak self] in
        self?.dataTableView.reloadData()
    }
}

我应该如何将 DispatchGroup 用于两个 url 请求？

How should I use DispatchGroup for two url requests?

swift

dispatch-queue