如何从特定位置查找string中的索引

我知道如何find如下的字符索引：

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

如何在特定位置后查找索引？

例如：myString =“abcdabcd”

我想得到第二个'd'= 7的索引

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

任何帮助？

Answer 1

尝试像这样：

 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 } }