如何从特定位置查找字符串中字符的索引 [英] how to find the index of a character in a string from specific position

问题描述

我知道如何找到如下字符的索引：

I know how to find an index of a character like the following:

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

    }

我如何查找索引在特定职位之后？

How can I look for an index after a specific position ?

例如：
myString =abcdabcd

example: myString="abcdabcd"

我想要得到第二个'd'= 7的索引

I would like to get the index of the second 'd' = 7

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

任何帮助？

推荐答案

尝试这样：

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
    }

}

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