如何检查Array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，当我运行此代码时，我收到以下错误：

Fatal error: Array index is out of range

。我想阻止它。

Answer 1

您可以检查有效数组索引的范围是否“限制”为 给定的闭合范围等于该范围：

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：

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

Answer 2

检查

ClosedRange<Int>

和

Range<Int>

请记住，

Range

不包括

upperBound

private extension Array {
    func contains(range: ClosedRange<Int>) -> Bool {
        indices.contains(range.lowerBound) && indices.contains(range.upperBound)
    }
}

private extension Array {
    func contains(range: Range<Int>) -> Bool {
        range.lowerBound >= 0 && range.upperBound <= count
    }
}