A Swift Int-subscript for Strings

Abstract - StringSubscripts.md

String subscripts

Implementation of string subscripts using Int.

var str = "😂😅😊😜😝"
str[0..<2] = ""
print(str)
// Prints "😊😜😝"

StringSubscript.swift

extension String {
    subscript(index: String.CharacterView.Index) -> Character {
        get { return self.characters[index] }
        set {
            self.characters.remove(at: index)
            self.characters.insert(newValue, at: index)
        }
    }
    
    subscript(range: Range<Index>) -> String {
        @warn_unused_result get { return String(self.characters[range]) }
        set { self.characters.replaceSubrange(range, with: newValue.characters) }
    }
    
    @warn_unused_result
    func getIndex(_ v: Int) -> Index {
        return self.index(startIndex, offsetBy: v)
    }
    
    @warn_unused_result
    func getIndexRange(_ r: CountableRange<Int>) -> Range<Index> {
        let start = getIndex(r.lowerBound)
        let end = index(start, offsetBy:  r.count)
        return start..<end
    }
    
    subscript(index: Int) -> Character {
        @warn_unused_result get { return self[getIndex(index)]     }
                            set { self[getIndex(index)] = newValue }
    }
    
    subscript(range: CountableRange<Int>) -> String {
        @warn_unused_result get { return self[getIndexRange(range)]     }
                            set { self[getIndexRange(range)] = newValue }
    }
}