ios - 如何从特定位置查找字符串中字符的索引

Question

我知道如何找到如下字符的索引:

func indexOfCharacter(myString:String, char: Character) -> Int {
        if let idx = find(myString, char) {
            return distance(self.startIndex, idx)
        }else{
            return -1;
        }

    }

如何查找特定位置后的索引？

例子:myString="abcdabcd"

我想得到第二个 'd' = 7 的索引

indexOfCharacter(myString,character : 'd',fromIndex: 4);

有什么帮助吗？

Answer 1

像这样尝试:

func indexOfCharacter(myString:String, char: Character,fromIndex: Int) -> Int {

    let sub = myString.substringFromIndex(advance(myString.startIndex, fromIndex))
    if let idx = find(sub, char) {
        return distance(sub.startIndex, idx) + fromIndex
    }else{
        return -1
    }

}

let myString = "abcdabcd"

indexOfCharacter(myString, "d", 4)   // 7

更新:Xcode 7.3 • Swift 2.2

func indexOfCharacter(myString:String, char: Character, fromIndex: Int) -> Int {

    let sub = myString.substringFromIndex(myString.startIndex.advancedBy(fromIndex))
    if let idx = sub.characters.indexOf(char){
        return sub.startIndex.distanceTo(idx) + fromIndex
    }else{
        return -1
    }

}