swift - 这段遗留 Swift 代码中 "SubSlice"的新等价物是什么？

Question

我正在查看 this legacy Swift code实现 Peter Norvig 的拼写检查器，并遇到了这段代码:

extension Array {
    subscript(r: RangeStart<Int>) -> SubSlice { return self[r.start..<self.endIndex] }
    subscript(r: RangeEnd<Int>) -> SubSlice { return self[self.startIndex..<r.end] }
}

我该如何重写它，以便 SubSlice 更新到现在应该的样子？

Answer 1

您正在寻找 ArraySlice<Element> :

struct RangeStart<I: ForwardIndexType> { let start: I }
struct RangeEnd<I: ForwardIndexType> { let end: I }

extension Array {
    subscript(r: RangeStart<Int>) -> ArraySlice<Element> { return self[r.start..<self.endIndex] }
    subscript(r: RangeEnd<Int>) -> ArraySlice<Element> { return self[self.startIndex..<r.end] }
}

/* example usage */
let foo = Array(0...10)
foo[RangeStart<Int>(start: 5)] // [5, 6, 7, 8, 9, 10]
foo[RangeEnd<Int>(end: 6)]     // [0, 1, 2, 3, 4, 5]

let bar = ["1", "2", "3", "4", "5"]
bar[RangeStart<Int>(start: 2)] // ["3", "4", "5"]
bar[RangeEnd<Int>(end: 3)]     // ["1", "2", "3"]