arrays - 如何检查Array是否包含ClosedRange？

在我用SWIFT 4.2编写的申请表中，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，会收到以下错误：Fatal error: Array index is out of range。我想阻止它。

最佳答案

可以检查有效数组索引的范围是否“钳制”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，相当于：

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