Replacing two ranges in a String simultaneously-CodePudding

Say you have a string that looks likes this:

let myStr = "Hello, this is a test String"

And you have two Ranges,

let rangeOne = myStr.range(of: "Hello") //lowerBound: 0, upperBound: 4
let rangeTwo = myStr.range(of: "this")  //lowerBound: 7, upperBound: 10

Now you wish to replace those ranges of myStr with new characters, that may not be the same length as their original, you end up with this:

var myStr = "Hello, this is a test String"

let rangeOne = myStr.range(of: "Hello")!
let rangeTwo = myStr.range(of: "this")!

myStr.replaceSubrange(rangeOne, with: "Bonjour") //Bonjour, this is a test String
myStr.replaceSubrange(rangeTwo, with: "ce") //Bonjourceis is a test String

Because rangeTwo is based on the pre-altered String, it fails to properly replace it.

I could store the length of the replacement and use it to reconstruct a new range, but there is no guarantee that rangeOne will be the first to be replaced, nor that rangeOne will actually be first in the string.

CodePudding user response：

The solution is the same as removing multiple items from an array by index in a loop.

Do it backwards

First replace rangeTwo then rangeOne

myStr.replaceSubrange(rangeTwo, with: "ce")
myStr.replaceSubrange(rangeOne, with: "Bonjour")

CodePudding user response：

This problem can be solved by shifting the second range based on the length of first the replaced string.

Using your code, here is how you would do it:

var myStr = "Hello, this is a test String"

let rangeOne = myStr.range(of: "Hello")!
let rangeTwo = myStr.range(of: "this")!

let shift = "Bonjour".count - "Hello".count

let shiftedTwo = myStr.index(rangeTwo.lowerBound, offsetBy: shift)..<myStr.index(rangeTwo.upperBound, offsetBy: shift)

myStr.replaceSubrange(rangeOne, with: "Bonjour") // Bonjour, this is a test String
myStr.replaceSubrange(shiftedTwo, with: "ce") // Bonjour, ce is a test String

CodePudding user response：

You can sort the range in descending order, then replace backwards, from the end to the start. So that any subsequent replacement will not be affect by the previous replacements. Also, it is safer to use replacingCharacters instead of replaceSubrange in case when dealing with multi-codepoints characters.

let myStr = "Hello, this is a test String"

var ranges = [myStr.range(of: "Hello")!,myStr.range(of: "this")!]
ranges.shuffle()
ranges.sort(by: {$1.lowerBound < $0.lowerBound}) //Sort in reverse order

let newWords : [String] = ["Bonjour