Creating A Substring | Swift 4

Question

How do I substring a string in swift 4.

I would like to convert:

"Hello, World!"

Into:

"Hello"

Answer 1

Swift has no built in function to make this easy so I wrote a simple extension to get the same functionality as other languages such as python which have really easy substring functions.

Extension

Outside your class, add this extension for strings.

extension String {
    func substring(start: Int, range: Int) -> String {
        let characterArray = Array(self)
        var tempArray:[Character] = []
        let starting = start
        let ending = start + range
        for i in (starting...ending) {
            tempArray.append(characterArray[i])
        }
        let finalString = String(tempArray)
        return finalString
    }
}

Usage

let myString = "Hello, World!"
print(myString.substring(start: 0, range: 4))

This prints:

"Hello"

How It Works

The extension works by turning the string into an array of separate characters then creates a loop which appends the desired characters into a new string which is determined by the function's parameters.

Thanks for stopping by. I hope apple add this basic functionality to their language soon! The above code is a bit messy so if anyone wants to clean it up then feel free!