arrays - 如何检查数组是否包含 ClosedRange？

Question

在我用 Swift 4.2 编写的应用程序中，我有以下代码:

let arrayOfIntegers = [2, 1, 9, 5, 4, 6, 8, 7]
let unknownLowerBound = 4
let unknownUpperBound = 20
let closedRange = ClosedRange<Int>(uncheckedBounds: (lower: unknownLowerBound,
                                                     upper: unknownUpperBound))
let subRange = arrayOfIntegers[closedRange]
subRange.forEach { print($0) }

您可以猜到，当我运行这段代码时，我收到了以下错误: fatal error :数组索引超出范围。我想阻止它。

Answer 1

您可以检查有效数组索引的范围是否“钳制”到给定的封闭范围等于该范围:

let array = [1, 2, 3, 4, 5, 6, 7, 8]
let closedRange = 4...20
if array.indices.clamped(to: Range(closedRange)) == Range(closedRange) {
    let subArray = array[closedRange]
    print(subArray)
} else {
    print("closedRange contains invalid indices")
}

或者，等价地:

if array.indices.contains(closedRange.lowerBound)
    && array.indices.contains(closedRange.upperBound) {
    // ...
}