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iOS Object-Oriented Swift Inheritance Overriding Methods

Alex Nelsen
PLUS
Alex Nelsen
Courses Plus Student 2,977 Points

There is some discrepancy between playground and the challenge.

So in my playground this works.

class Button {

var width: Double
var height: Double

init(width: Double, height: Double) {
    self.width = width
    self.height = height
}
func incrementBy(points: Double) -> (Double, Double)  {
   self.width = width + points
    self.height = height + points
    return( width, height)
}

} var newButton = Button(width: 3, height: 10) newButton.incrementBy(7)

class RoundButton: Button { var cornerRadius: Double = 5.0

override func incrementBy(points: Double = 7.0) -> (Double, Double)  {

    return super.incrementBy(points)
}

}

let rounded = RoundButton(width: 50, height: 50) rounded.incrementBy() rounded.incrementBy()

In the challenge I edited the super class method to return width and height since the method seems to create the same results as my method and return super.incrementBy(points) will keep it DRY. It fails in the challenge.

Any help would be appreciated.

Button.swift
class Button {
  var width: Double
  var height: Double

  init(width:Double, height:Double){
    self.width = width
    self.height = height
  }

  func incrementBy(points: Double = 0.0) -> (Double, Double){
    width += points
    height += points
    return (width, height)
  }
}

class RoundButton: Button {
  var cornerRadius: Double = 5.0
   override func incrementBy(points: Double = 7.0) -> (Double, Double)  {

        return super.incrementBy(points)
    }


}

1 Answer

Michael Reining
Michael Reining
10,101 Points

Hi Alex,

There are a couple of mistakes in your code.

  1. Do not change the main Button class.

  2. Set the parameter value to 7 inside the function so that regardless of what value you pass in, you always increment it by seven

  3. There is no need to return a value from the function

The final result then looks like this.

class Button {
    var width: Double
    var height: Double

    init(width:Double, height:Double){
        self.width = width
        self.height = height
    }

    func incrementBy(points: Double) { // don't change Button Class
        width += points
        height += points
    }
}

class RoundButton: Button {
    var cornerRadius: Double = 5.0
    override func incrementBy( var points: Double)  { // mark parameter with var to make it mutable
        points = 7
        self.width += points
        self.height += points
    }


}

I hope that helps,

Mike

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https://itunes.apple.com/app/code!-learn-how-to-program/id1032546737?mt=8

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Alex Nelsen
Alex Nelsen
Courses Plus Student 2,977 Points

Yes that helped to solve the challenge. But why did Amit in his example go and change the method to include a return. Your method is simpler I feel.