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iOS Intermediate Swift 2 Extensions and Protocols Extending a Native Type

Posted by Stuart Robertson
Stuart Robertson
Courses Plus Student 1,296 Points

Extending With Native Types Code Challenge

Hey, I was trying to make a function out of this, but I can't remember how or if there is a way to convert one type to another. If anyone knows how please tell me, and also if I am on the right track or going about this completely wrong. Thanks!

types.swift 
// Extending A Native Type

extension String {

    var add: String {
        func AddingWithStringAndInts(let integerInt: Int) -> String {
            return self + integerInt
        }
    }
}

2 Answers

jcorum
jcorum
71,830 Points

First, they want a function, not a variable. Second, it needs to take an Int and return one, but since nil is a possible return value it has to be an optional Int. Third, you need to convert the String to an Int, and you need optional binding, because the String may be something like "a" rather than "2", i.e., a String that could not be converted.

extension String {
  func add(x: Int) -> Int? {
    if let y = Int(self) {
      return y + x
    } else {
      return nil
    }
  }
}
Stuart Robertson
Stuart Robertson
Courses Plus Student 1,296 Points

Oh thanks for that, much appreciated!

Jens Hagfeldt
Jens Hagfeldt
16,548 Points
Jens Hagfeldt
Jens Hagfeldt
16,548 Points

Thanks jcorum, that helped me a lot!

larry sigo
larry sigo
4,067 Points
larry sigo
larry sigo
4,067 Points 
 extension String {
    func add (value: Int) -> Int?{
        //return an integer value if the string can be converter to an integer
        if let intValue = Int(self) {
             return intValue  + value
        }else{
            return nil
        }
    }
}