Format String left of multiple characters in Swift 5?

Question

I have some Strings that vary in length but always end in "listing(number)"

myString = 9AMnep8MAziUCK7VwKF51mXZ2listing28

.

I want to get the String without "listing(number)":

9AMnep8MAziUCK7VwKF51mXZ2

.

Methods I've tried such as .index(of: ) only let you format based off one character. Any simple solutions?

Answer 1

A possible solution is to search for the substring with Regular Expression and remove the result (replace it with empty string)

let myString = "9AMnep8MAziUCK7VwKF51mXZ2listing28"
let trimmedString = myString.replacingOccurrences(of: "listing\\d+$", with: "", options: .regularExpression)

• \\d+ searches for one ore more digits
• $ represents the end of the string

Alternatively without creating a new string

var myString = "9AMnep8MAziUCK7VwKF51mXZ2listing28"
if let range = myString.range(of: "listing\\d+$", options: .regularExpression) {
    myString.removeSubrange(range)
}

Answer 2

Another option is to split the string in parts with "listing" as separator

let result = myString.components(separatedBy: "listing").first

Answer 3

So to solve your issue find the code below with few comments written to try and explain each steps have taken. kindly note i have modified or arrived at this solution using this links as a guide.

1. https://stackoverflow.com/a/40070835/6596443

2. https://www.dotnetperls.com/substring-swift

   extension String {
       //
       // Paramter  inputString: This is the string you want to manipulate
       // Paramter- startStringOfUnwanted: This is the string you want to start the removal or replacement from
       //return : The expected output you want but can be emptystring if unable to
   
       static func trimUnWantedEndingString(inputString: String,startStringOfUnwanted: String) -> String{
           //Output string
           var outputString: String?
           //Getting the range based on the string content
           if let range = myString.range(of: startStringOfUnwanted) {
               //Get the lowerbound of the range
               let lower = range.lowerBound
               //Get the upperbound of the range
               let upper = range.upperBound
               //Get the integer position of the start index of the unwanted string i added plus one to ensure it starts from the right position
               let startPos = Int(myString.distance(from: myString.startIndex, to: lower))+1
               //Get the integer position of the end index of the unwanted string i added plus one to ensure it starts from the right position
               let endPos =  Int(myString.distance(from: myString.startIndex, to: upper))+1
               //Substract the start int from the end int to get the integer value that will be used to get the last string i want to stop trimming at
               let endOffsetBy = endPos-startPos
               //get thes string char ranges of values
               let result = myString.index(myString.startIndex, offsetBy: 0)..<myString.index(myString.endIndex, offsetBy: -endOffsetBy)
               //converts the results to string or get the string representation of the result and then assign it to the OutputString
               outputString = String(myString[result]);
           }
           return outputString ?? "";
       }
   }
   let myString = "9AMnep8MAziUCK7VwKF51mXZ2listing28"
   String.trimUnWantedEndingString(inputString: myString, startStringOfUnwanted:"listing")