不存储值的数组

Question

我从解析后端获取值并使用它们来创建数组，但是没有任何数据存储在其中。有人可以告诉我我做错了什么吗？行：让的DataEntry = ChartDataEntry（值：值[I]，xIndex：ⅰ）还给 “索引超出范围”

var fattyArray: [Double] = [] 

override func viewDidLoad() { 
    super.viewDidLoad() 

    let innerQuery = PFUser.query() 
    innerQuery!.whereKey("objectId", equalTo: "VTieywDsZj") 
    let query = PFQuery(className: "BodyFat") 
    query.whereKey("UserID", matchesQuery: innerQuery!) 
    query.findObjectsInBackgroundWithBlock { 
     (percentages: [PFObject]?, error: NSError?) -> Void in 
     if error == nil { 
      print("Successful, \(percentages!.count) retrieved") 
      if let percentage = percentages as [PFObject]! { 
       for percentage in percentages! { 
        print(percentage["BodyFatPercentage"]) 
     self.fattyArray.append(percentage["BodyFatPercentage"].doubleValue) 
        print(self.fattyArray) 
       } 
      } 
     } else { 
      print("\(error?.userInfo)") 
     } 
    } 

    let months = ["Jan", "Feb", "Mar", "Apr", "May", "Jun"] 
    let unitsSold = fattyArray 

    setChart(months, values: unitsSold) 

} 

func setChart(dataPoints: [String], values: [Double]) { 

    var dataEntries: [ChartDataEntry] = [] 

    for i in 0..<dataPoints.count { 
     let dataEntry = ChartDataEntry(value: values[i], xIndex: i) 
     dataEntries.append(dataEntry) 
    } 

Answer 1

有两个问题这里：

1. 的一个问题findObjectsInBackgroundWithBlock是异步运行的，即fattyArray直到后面没有附加值。您应该将调用setChart的代码移入findObjectsInBackgroundWithBlock闭包。

   query.findObjectsInBackgroundWithBlock { percentages, error in 
       if error == nil { 
        // build your array like you did in your question 
   
        // but when done, call `setChart` here 
   
        let months = ["Jan", "Feb", "Mar", "Apr", "May", "Jun"] 
        let unitsSold = fattyArray 
   
        setChart(months, values: unitsSold) 
       } else { 
        print("\(error?.userInfo)") 
       } 
   } 
   
   // but not here 
   
   // let months = ["Jan", "Feb", "Mar", "Apr", "May", "Jun"] 
   // let unitsSold = fattyArray 
   // 
   // setChart(months, values: unitsSold) 
   

2. 你setChart程序给你一个“索引超出范围”，因为您是通过迭代dataPoints，但values数组中查找值误差。我在这里看不到任何内容，以确保months与fattyArray中的条目数相同。很显然，如果你修正了第一点，你就有更好的机会运行它（因为在数据被完全检索之前你实际上不会生成图表），但是我仍然没有看到任何东西这里保证findObjectsInBackgroundWithBlock将返回至少六个条目。