Question

我需要按以下顺序运行三个函数：

从Firebase收集整数，将它们放入数组中，然后计算总和。完成后...
收集与Firebase不同的整数值。完成后...
第三个函数从函数2获取值，然后从函数1减去它。

我知道我需要使用完成处理程序，但是在语法等方面需要一些帮助。

///第一个函数从Firebase获取整数并将其求和：

func LoadPointsCompleted(completion: @escaping(_ sumOfPointsCompleted:Int) -> Int){

    self.challengeList.removeAll()

    databaseReference = Database.database().reference()

    let userID = Auth.auth().currentUser?.uid

    let refChallenges = Database.database().reference(withPath: "Challenges").child(userID!).queryOrdered(byChild: "Status").queryEqual(toValue: "Complete")

    refChallenges.observeSingleEvent(of: .value, with: { (snapshot) in

        //if the reference have some values
        if snapshot.childrenCount > 0 {

            //clearing the list
            self.challengeList.removeAll()



            //iterating through all the values
            for Challenges in snapshot.children.allObjects as! [DataSnapshot] {
                //getting values
                let challengeObject = Challenges.value as? [String: AnyObject]
                let Points = challengeObject?["Points"] as! Int

                //creating challenge object with model and fetched values
                let challenge = pointsModel(Points: (Points as Int?)!)

                //appending it to list
                self.challengeList.append(challenge)


                let sumOfPointsCompleted = self.challengeList.reduce(0) {$0 + $1.Points}

                let sumOfPointsCompletedString = String(sumOfPointsCompleted)
                self.Calc_Earned.text = sumOfPointsCompletedString

                completion(sumOfPointsCompleted)

            }

        }

    }

    )}

///第二个功能只是从Firebase的另一个位置获取一个整数值

func loadPointsRedeemed(completion: @escaping (_ Points_Redeem: Int) -> Int) {


    databaseReference = Database.database().reference()

    let userID = Auth.auth().currentUser?.uid

    databaseReference.child("Users").child(userID!).observe(DataEventType.value, with: { (snapshot) in

        let value = snapshot.value as? NSDictionary

        // let Points_Earn = value?["Points_Earned"] as? String ?? ""
        let Points_Redeem = value?["Points_Redeemed"] as! Int


        // self.Points_Earned.text = Points_Earn

        let points_redeemedString = String(Points_Redeem)
        self.Points_Redeemed.text = points_redeemedString

        // let pointsRedeemedAs = Points_Redeem

        completion(Points_Redeem)

        // Do any additional setup after loading the view.
    }

)}

//这第三个函数只是从前两个函数中获取值并将其相减

 func BalanceOfPoints(){

    let a = LoadPointsCompleted()
    let b = loadPointsRedeemed()


    let balance = a - b
    let balanceString = String(balance)

    self.Points_Balance.text = balanceString

}

但是，在第三个函数“ BalanceOfPoints”中出现如下错误：

在调用中缺少参数'completion'的参数-插入'completion：<（Int）-> Int>'

我不知道我第一次按以下方式启动函数时语法是否正确：

func LoadPointsCompleted(completion: @escaping(_ sumOfPointsCompleted:Int) -> Int){

和...

func loadPointsRedeemed（完成情况：@转义（_ Points_Redeem：Int）-> Int）{

有人可以帮忙吗？预先感谢。

Answer 1

docker-compose run image bash -c "cd /path/to/somewhere && python a.py"以闭包作为参数（完成处理程序）

您可以给它一个LoadPointsCompleted完成处理程序

nil

或给它一个处理程序

LoadPointsCompleted(completion: nil)

但是您在LoadPointsCompleted() { sumOfPointsCompleted in return <#some Int#> }中的逻辑似乎有点错，因为BalanceOfPoints和LoadPointsCompleted同时被依次调用，并且实际上并没有返回loadPointsRedeemed函数的完成处理程序会执行。例如，Int可以更改为completion(sumOfPointsCompleted)，但请确保那不是您想要的。

我将这两个功能的签名更改为

let a = completion(sumOfPointsCompleted)

和

func LoadPointsCompleted(completion: @escaping(_ sumOfPointsCompleted:Int) -> Void){

然后在func loadPointsRedeemed(completion: @escaping (_ Points_Redeem: Int) -> Void) {中代替

BalanceOfPoints

但是请注意，func BalanceOfPoints(){ LoadPointsCompleted() { sumOfPointsCompleted in loadPointsRedeemed() { Points_Redeem in let balance = sumOfPointsCompleted - Points_Redeem let balanceString = String(balance) self.Points_Balance.text = balanceString } } }现在是一个异步函数。

不确定您的问题中的步骤1和步骤2是否可以并行执行，但是看起来可以并行执行，但是按照此答案中的顺序，它们是按顺序排列的

使用完成处理程序按顺序执行操作

1 个答案: