问For循环以随机顺序追加数组

EN

func updateGraphData(timeInterval: Int){
    if selectedCurrency1 != nil && selectedCurrency2 != nil { // checking if both currencies have been selected 
        self.xAxisData.removeAll() // removing some default values

        for i in 1...timeInterval { // don't know exactly if i'm doing this the optimal way?
            print("passed")
            let date = Date()
            let dateComponents = Calendar.current.dateComponents([.month, .day,.year], from: date) //getting the the year(again, just to see if it's working)
            historyURL = "http://api.fixer.io/\(dateComponents.year!.description)-03-0\(String(i))?base=\(selectedCurrency1!.rawValue)" //modifying the url to my needs 


            Alamofire.request(historyURL, method: .get).responseJSON { // requesting data
                response in
                if response.result.isSuccess{
                    let json = JSON(response.result.value!)
                    self.xAxisData.append(json["rates"] [self.selectedCurrency2!.rawValue].doubleValue) // using SwiftyJSON btw to convert, but shouldn't this in theory append in the correct order?
                    print(json["date"].stringValue) // printing out the date


                }
                else{
                    print("Error \(String(describing: response.result.error))")
                }
        }

    }
    }
}

    []
2017-03-02
2017-03-03
2017-03-01
2017-03-03
2017-03-03
2017-03-06
2017-03-07
[4.5359999999999996, 4.5316000000000001, 4.4739000000000004, 4.5316000000000001, 4.5316000000000001, 4.5133000000000001, 4.4844999999999997]