Use function from one class in another class in Swift

Question

So lets say I have a class called Math

class Math{

    func add(numberOne: Int, numberTwo: Int) -> Int{

        var answer: Int = numberOne + numberTwo
        return answer
    }

In this class there is a function which allows the user to add two numbers.

I now have another class which is a subclass of a UIViewController and I want to use the add function from the Math class, how do I do this?

class myViewController: UIViewController{

    //Math.add()???

}

`var answer` should be `let answer` – 54 69 6D Jul 15 '16 at 19:16 — 54 69 6D, Jul 15 '16 at 19:16

score 20 · Accepted Answer · answered Jul 23 '14 at 21:49

20

If you want to be able to say Math.add(...), you'll want to use a class method - just add class before func:

class Math{

    class func add(numberOne: Int, numberTwo: Int) -> Int{

        var answer: Int = numberOne + numberTwo
        return answer
    }
}

Then you can call it from another Swift class like this:

Math.add(40, numberTwo: 2)

To assign it to a variable i:

let i = Math.add(40, numberTwo: 2) // -> 42

answered Jul 23 '14 at 21:49

Undo

25,519
37
106
129

Thank you, but why did you take out the first argument name numberOne and kept the second one numberTwo in the function call? – Stephen Fox Jul 23 '14 at 21:51
1

It's a Swift nuance, @StephenFox. Swift leaves out the first parameter label to any function that isn't an init function. I explain it further in [this answer](http://stackoverflow.com/questions/24815832/when-are-argument-labels-required-in-swift/24815909#24815909). – Undo Jul 23 '14 at 21:52

score 3 · Answer 2 · edited Jul 24 '14 at 10:33

Use class keyword before add function to make it class function.

You can use

class Math{
    class func add(numberOne: Int, numberTwo: Int) -> Int{

        var answer: Int = numberOne + numberTwo
        return answer
    }
}

class myViewController: UIViewController{

    //Math.add()???
    //call it with class `Math`
    var abc = Math.add(2,numberTwo:3)
}


var controller = myViewController()
controller.abc  //prints 5

This code is from playgound.You can call from any class.

score 0 · Answer 3 · answered Oct 12 '17 at 10:45

Swift 4:

class LoginViewController: UIViewController {
//class method
@objc func addPasswordPage(){
  //local method  
  add(asChildViewController: passwordViewController)
    }

func  add(asChildViewController viewController: UIViewController){

    addChildViewController(viewController)
  }
}

class UsernameViewController: UIViewController {

let login = LoginViewController()
override func viewDidLoad() {
    super.viewDidLoad()
   //call login class method
   login.addPasswordPage()

  }
}

Use function from one class in another class in Swift

3 Answers3

Linked