“收集相应的.”Swift 3升级错误

Question

这是一个预Xcode-8快速电话..。

func gappizeAtDoubleNewlines()
    {
    let t = self.text!
    var index = t.startIndex
    var follow = index.advancedBy(1)

    for i in 0 ..< (t.characters.count-4)
        {
        let r = index ... follow
        if ( t.substringWithRange(r) == "\n\n" )
            { alterLineGapHere(i) }

        index = index.advancedBy(1)
        follow = index.advancedBy(1)
        }
    }

通过自动升级到Swift3，我得到了这些错误.

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在文本中，

func gappizeAtDoubleNewlines()
    {
    let t = self.text!
    var index = t.startIndex
    var follow = <#T##Collection corresponding to `index`##Collection#>.index(index, offsetBy: 1)

    for i in 0 ..< (t.characters.count-4)
        {
        let r = index ... follow
        if ( t.substring(with: r) == "\n\n" )
            { alterLineGapHere(i) }

        index = <#T##Collection corresponding to `index`##Collection#>.index(index, offsetBy: 1)
        follow = <#T##Collection corresponding to `index`##Collection#>.index(index, offsetBy: 1)
        }
    }

Swift3中的解决方案是什么?？

Answer 1

参见SE-0065：“集合移动其索引” -在本例中，您只需将编辑器占位符替换为t

func gappizeAtDoubleNewlines() {

    let t = self.text!
    var index = t.startIndex

    // Note that because substring(by:) takes a Range<String.Index>, rather than
    // a ClosedRange, we have to offset the upper bound by one more.
    var follow = t.index(index, offsetBy: 2)

    for i in 0 ..< (t.characters.count-4) {
        let r = index ..< follow
        if (t.substring(with: r) == "\n\n") {
            alterLineGapHere(i)
        }

        index = t.index(index, offsetBy: 1)
        follow = t.index(follow, offsetBy: 1)
    }
}

尽管注意到String本身并不是Collection，但它只是实现了一些方便的方法来为转发到t.characters (即Collection )的索引进行索引。