Swift3.0无法将"ClosedRange <Index>"类型的值转换为"Range <Index>"类型

Question

我正在尝试将Swift 2.3迁移到3.0并且转换后面临此问题.有什么建议我做错了.

Swift 3.0:

override func setValue(_ value: AnyObject?, forKey key: String) {
    let uppercasedFirstCharacter = String(key.characters.first!).uppercased()
    let range = key.startIndex...key.index(key.startIndex, offsetBy: 0)
    let selectorString = key.replacingCharacters(in: range, with: uppercasedFirstCharacter)

    let selector = NSSelectorFromString("set\(selectorString):")
    let responds = self.responds(to: selector)

    if !responds {
        return
    }

错误:

let selectorString = key.replacingCharacters(in:range,with:uppercasedFirstCharacter)

Cannot convert value of type 'ClosedRange<Index>' (aka 'ClosedRange<String.CharacterView.Index>') to expected argument type 'Range<Index>' (aka 'Range<String.CharacterView.Index>')

原始代码:Swift 2.3

override func setValue(value: AnyObject?, forKey key: String) {
    let uppercasedFirstCharacter = String(key.characters.first!).uppercaseString

    let range = key.startIndex...key.startIndex.advancedBy(0)
    let selectorString = key.stringByReplacingCharactersInRange(range, withString: uppercasedFirstCharacter)

    let selector = NSSelectorFromString("set\(selectorString):")
    let responds = self.respondsToSelector(selector)

    if !responds {
        return
    }

Answer 1

您可以使用..<而不是...for range来Range<Index>代替ClosedRange<Index>,在这种情况下,调用stringByReplacingCharactersInRange(...)不会产生错误(注意offsetBy增加1).

let range = key.startIndex..<key.index(key.startIndex, offsetBy: 1)
// range is now type Range<Index>

现在,我可能错了,但似乎你只是希望成为第一个字符大写selectorString的版本key.您的范围解决方案的另一种方法是,您可以使用String扩展解决方案,如下所示:

extension String { 
   var firstCharacterUppercased: String {
        guard case let c = self.characters,
                   let c1 = c.first else { return self }
        return String(c1).uppercased() + String(c.dropFirst())
    }
}

/* example usage */
let key = "fooBar"
let selectorString = key.firstCharacterUppercased

print(selectorString) // FooBar