Swift 3.0让这个更加冗长:

let string = "Hello.World"
let needle: Character = "."
if let idx = string.characters.index(of: needle) {
    let pos = string.characters.distance(from: string.startIndex, to: idx)
    print("Found \(needle) at position \(pos)")
}
else {
    print("Not found")
}

扩展:

extension String {
    public func index(of char: Character) -> Int? {
        if let idx = characters.index(of: char) {
            return characters.distance(from: startIndex, to: idx)
        }
        return nil
    }
}

在Swift 2.0中，这变得更加容易:

let string = "Hello.World"
let needle: Character = "."
if let idx = string.characters.indexOf(needle) {
    let pos = string.startIndex.distanceTo(idx)
    print("Found \(needle) at position \(pos)")
}
else {
    print("Not found")
}

扩展:

extension String {
    public func indexOfCharacter(char: Character) -> Int? {
        if let idx = self.characters.indexOf(char) {
            return self.startIndex.distanceTo(idx)
        }
        return nil
    }
}

斯威夫特1。x实现:

对于纯Swift解决方案，可以使用:

let string = "Hello.World"
let needle: Character = "."
if let idx = find(string, needle) {
    let pos = distance(string.startIndex, idx)
    println("Found \(needle) at position \(pos)")
}
else {
    println("Not found")
}

作为String的扩展:

extension String {
    public func indexOfCharacter(char: Character) -> Int? {
        if let idx = find(self, char) {
            return distance(self.startIndex, idx)
        }
        return nil
    }
}

斯威夫特3

extension String {
        func substring(from:String) -> String
        {
            let searchingString = from
            let rangeOfSearchingString = self.range(of: searchingString)!
            let indexOfSearchingString: Int = self.distance(from: self.startIndex, to: rangeOfSearchingString.upperBound )
            let trimmedString = self.substring(start: indexOfSearchingString , end: self.count)
            
            return trimmedString
        }
        
    }

extension String{
    func contains(find: String)->Bool{
        return self.range(of: find) != nil
    }
}
 
func check(n:String, h:String)->Int{
    let n1 = n.lowercased()
    let h1 = h.lowercased()//lowercase to make string case insensitive
    var pos = 0 //postion of substring
    if h1.contains(n1){
       // checking if sub string exists
        if let idx = h1.firstIndex(of:n1.first!){
             let pos1 = h1.distance(from: h1.startIndex, to: idx)
           pos = pos1
        }
        return pos
    }
    else{
        return -1
    }
}
 
print(check(n:"@", h:"hithisispushker,he is 99 a good Boy"))//put substring in n: and string in h

在swift 2.0中

var stringMe="Something In this.World"
var needle="."
if let idx = stringMe.characters.indexOf(needle) {
    let pos=stringMe.substringFromIndex(idx)
    print("Found \(needle) at position \(pos)")
}
else {
    print("Not found")
}

在Swift 2中获取子字符串的索引:

let text = "abc"
if let range = text.rangeOfString("b") {
   var index: Int = text.startIndex.distanceTo(range.startIndex) 
   ...
}

我玩以下的游戏

extension String {
    func allCharactes() -> [Character] {
         var result: [Character] = []
         for c in self.characters {
             result.append(c)
         }
         return 
    }
}

直到我理解提供的一个，现在它只是字符数组

和

let c = Array(str.characters)