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
        }
        
    }

String是NSString的桥接类型，add

import Cocoa

到你的swift文件，并使用所有“旧”的方法。

    // Using Swift 4, the code below works.
    // The problem is that String.index is a struct. Use dot notation to grab the integer part of it that you want: ".encodedOffset"
    let strx = "0123456789ABCDEF"
    let si = strx.index(of: "A")
    let i = si?.encodedOffset       // i will be an Int. You need "?" because it might be nil, no such character found.

    if i != nil {                   // You MUST deal with the optional, unwrap it only if not nil.
        print("i = ",i)
        print("i = ",i!)            // "!" str1ps off "optional" specification (unwraps i).
            // or
        let ii = i!
        print("ii = ",ii)

    }
    // Good luck.

在思考方面，这可能被称为反转。你会发现世界是圆的而不是平的。“你真的不需要知道角色的索引来处理它。”作为一名C程序员，我发现这也很难接受! 你的行“let index = letters.characters.indexOf("c")!”本身就足够了。 例如，要去掉c，你可以用…(操场粘贴)

    var letters = "abcdefg"
  //let index = letters.rangeOfString("c")!.startIndex //is the same as
    let index = letters.characters.indexOf("c")!
    range = letters.characters.indexOf("c")!...letters.characters.indexOf("c")!
    letters.removeRange(range)
    letters

然而，如果你想要一个索引，你需要返回一个实际的index而不是Int值，因为Int值对于任何实际使用都需要额外的步骤。这些扩展返回一个索引，一个特定字符的计数，以及这个游乐场插件代码将演示的范围。

extension String
{
    public func firstIndexOfCharacter(aCharacter: Character) -> String.CharacterView.Index? {

        for index in self.characters.indices {
            if self[index] == aCharacter {
                return index
            }

        }
        return nil
    }

    public func returnCountOfThisCharacterInString(aCharacter: Character) -> Int? {

        var count = 0
        for letters in self.characters{

            if aCharacter == letters{

                count++
            }
        }
        return count
    }


    public func rangeToCharacterFromStart(aCharacter: Character) -> Range<Index>? {

        for index in self.characters.indices {
            if self[index] == aCharacter {
                let range = self.startIndex...index
                return range
            }

        }
        return nil
    }

}



var MyLittleString = "MyVery:important String"

var theIndex = MyLittleString.firstIndexOfCharacter(":")

var countOfColons = MyLittleString.returnCountOfThisCharacterInString(":")

var theCharacterAtIndex:Character = MyLittleString[theIndex!]

var theRange = MyLittleString.rangeToCharacterFromStart(":")
MyLittleString.removeRange(theRange!)

这对我很有效，

var loc = "abcdefghi".rangeOfString("c").location
NSLog("%d", loc);

这也奏效了，

var myRange: NSRange = "abcdefghi".rangeOfString("c")
var loc = myRange.location
NSLog("%d", loc);

如果你想使用熟悉的NSString，你可以显式地声明它:

var someString: NSString = "abcdefghi"

var someRange: NSRange = someString.rangeOfString("c")

我还不确定如何在Swift中做到这一点。