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

问题描述

我正在尝试在Swift 3中建立一个范围，该范围已经在Swift 2中存在，但它一直给我这个错误: String may not be indexed with 'Int', it has variable size elements

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<Index>?

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，集合移动其索引"，请参见 关于集合和指数的新模型

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

在字符串上调用

方法，以根据 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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