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iOS Intermediate Swift 2 Extensions and Protocols Extending a Native Type

Stuck on string extension challenge

don't know how to make the method add to a string

// Enter your code below
 extension String {

    func add(val: Int) -> Int {
        return self + add(val) ???

1 Answer

Good start so far.

You want to try and convert "self" (which is a String) to a Int first before adding it to the provided value. If "self" cannot be converted to a number, then you can return a nil.

extension String {
  func add(value: Int) -> Int? {
    if let stringAsNumber = Int(self) {
      return stringAsNumber + value
    } else {
      return nil