无法在 Swift 3 中创建范围 [英] Can't create a range in Swift 3

问题描述

我试图在 Swift 3 中创建一个我在 Swift 2 中已经拥有的范围，但它一直给我这个错误:字符串不能用'Int'索引，它有可变大小的元素

I am trying to make a range in Swift 3 that I already had in Swift 2 but it keeps giving me this error: String may not be indexed with 'Int', it has variable size elements

这是我的代码:

let range = expireRange!.startIndex.advancedBy(n: 7) ..< expireRange!.startIndex.advancedBy(n: 16)

expiredRange 是 Range?

expiredRange is a Range<Index>?

在 Swift 2 中，我有:

In Swift 2, I had:

let range = expireRange!.startIndex.advancedBy(7)...expireRange!.startIndex.advancedBy(16)

推荐答案

在 Swift 3 中，Collections move their index"，参见集合和索引的新模型关于 Swift 进化.

In Swift 3, "Collections move their index", see A New Model for Collections and Indices on Swift evolution.

以下是字符串范围和索引的示例:

Here is an example for String ranges and indices:

let string = "ABCDEFG"
if let range = string.range(of: "CDEF") {
    let lo = string.index(range.lowerBound, offsetBy: 1)
    let hi = string.index(range.lowerBound, offsetBy: 3)
    let subRange = lo ..< hi
    print(string[subRange]) // "DE"
}

public func index(_ i: Index, offsetBy n: IndexDistance) -> Index

方法在字符串上被调用来计算新的索引范围(现在具有属性 lower/upperBound 而不是start/endIndex).

method is called on the string to calculate the new indices from the range (which has properties lower/upperBound now instead of start/endIndex).

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