无法使用 'NSNumber' 类型的参数调用 'init' (Swift)

Question

我正在尝试使用 'weights' 数组通过以下获取请求填充图表。但是我收到错误消息“无法使用 'NSNumber' 类型的参数调用 'init'，我不知道为什么。'weights' 数组应该是 UInt16 数组。

var weights : [Int16] = []


func weightFetchRequest() -> NSFetchRequest {
            let appDelegate = UIApplication.sharedApplication().delegate as AppDelegate
            let managedContext = appDelegate.managedObjectContext!
            let fetchRequest = NSFetchRequest(entityName: "Assessment")
            fetchRequest.sortDescriptors = [NSSortDescriptor(key: "nsDateOfAssessment", ascending: true)]
            var error: NSError?

            let fetchedResults = managedContext.executeFetchRequest(fetchRequest, error: &error) as [Assessment]?

            if let assessments = fetchedResults {
                let weightss = assessments.map { assessment in assessment.weight }

                weights = weightss

                println(weights)
                println(weightss)
            }
            return fetchRequest
        }

func lineChartView(lineChartView: JBLineChartView!, verticalValueForHorizontalIndex horizontalIndex: UInt, atLineIndex lineIndex: UInt) -> CGFloat {
        if (lineIndex == 0) {
            return CGFloat(weights[Int16(horizontalIndex)] as NSNumber) //Error here
        }
        return 0
    }

Answer 1

行中有两个问题

return CGFloat(weights[Int16(horizontalIndex)] as NSNumber)

weights[Int16(horizontalIndex)] 无法编译，因为 Int16 不能是数组下标。应该是 weights[Int(horizontalIndex)].
weights[...] as NSNumber 无法编译，因为 固定大小 整数类型和 NSNumber 之间没有自动桥接，应该是 NSNumber(short: weights[...]).

所以这将编译并工作：

return CGFloat(NSNumber(short: weights[Int(horizontalIndex)]))

不过中间没必要用NSNumber，可以简化为

return CGFloat(weights[Int(horizontalIndex)])

无法使用 'NSNumber' 类型的参数调用 'init' (Swift)

Cannot invoke 'init' with argument of type 'NSNumber' (Swift)

ios

arrays

swift

int

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