Remove last n occurrences of a substring in a string in Swift

This tutorial will see how to remove the last n occurrences of a substring in a string in Swift. The substring is part of the parent string.

Algorithm

• Step 1: Import the foundation library. The Foundation framework is a standard library in swift that provides all the basic functionality and classes required for application building.
• Step 2: Create the function to remove the last n occurrences of a substring from the main string with a return data type of string.
  The parameters of the functions are:
  1. target: It is the substring that we want to delete from the parent string.
  2. string: It is the parent string i.e. input string.
  3. count: It is an integer that represents the number of last occurrences of the substring i.e. n.
• Step 3: Divide the parent string into an array of substrings using the components method.
  string.components(separatedBy: target): This method separates the parent string into substrings by deleting the target values in between.
• Step 4: Then remove the last n(count) components from the array formed before. This will delete the last n substrings from the substring array. This task can be done using the dropLast method.
  array.dropLast(count): This method removes the last count number of elements from an array. And returns the remaining array.
• Step 5: Then join the array elements using  joined method again to form the string and return it to the function.
  array.joined(separator: target): This method join the array elements by placing the target element in between to form a string.
  Swift Code to remove the last n occurrences of a substring in a string

  Here is the swift code to remove the last n occurrences of a substring in the string.

  import Foundation
  
  func removeLastOccurrences(of target: String, in string: String, count: Int) -> String 
  {
      let components = string.components(separatedBy: target)
      let filteredComponents = components.dropLast(count)
      return filteredComponents.joined(separator: target)
  }
  
  let input = "Hello world world world"
  let output = removeLastOccurrences(of: "world", in: input, count: 2)
  print(output)

  Output:

  Hello world