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iOS Object-Oriented Swift Classes and Objects Classes and Their Methods

Posted by tytyty
tytyty
4,974 Points

classes and methods challenge

OMG Even though I am comfortable with class methods I spent hours trying to figure out the calculation in the method LOL This wording threw me for a loop hehe "(Within the method add points to the width and height properties)." I couldn't figure out if you meant the word "points" or to actually ADD pixel points in a designator init after the class object.

class Button {
    var width: Double
    var height: Double

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

    func incrementBy(points: Double) {
        width = (width + points) // hated this!!
        height = (height + points) // hated this!!
    }

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

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

3 Answers

William Li
PLUS
William Li
Courses Plus Student 26,868 Points
William Li
William Li
Courses Plus Student 26,868 Points

You're on the right track. Here's the correction you should make to your incrementBy method.

  func incrementBy(points: Double) {
    self.width += points
    self.height += points
  }

In your original code

        width = (width + points) // hated this!!
        height = (height + points) // hated this!!

incrementBy method has no idea what width or height is, because when you write them like that, the method will assume that they're function parameters you pass in, but since the only parameter you pass in is points, incrementBy method doesn't know what to do and where width or height come from, thus give you compile-time error. Use self.width, self.height to refer to the width and height property of the object and incrementBy won't be complaining.

tytyty
tytyty
4,974 Points

oh thanks! We haven't been taught that syntax on the iOS track I'm on. I mean using that operator within an init method.

In my challenge with my code I got a success message so I think it was just looking for the basic structure like I had and then I guess in later lessons we'll be doing what you showed me.

Thanks Will

Mohsen Lotfi
Mohsen Lotfi
2,694 Points
Mohsen Lotfi
Mohsen Lotfi
2,694 Points

doing what William suggested but i,m getting compiler error

Binary operator '+=' cannot be applied to two Double operands

class Button {
    let width: Double
    let height: Double

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

    func incrementBy(points: Double) {
        self.width += width + points
        self.height += height + points
    }

}
tytyty
tytyty
4,974 Points
tytyty
tytyty
4,974 Points

Mohsen, you are adding an extra width and height. 

func incrementBy(points: Double) {
    self.width += points // remove the word width
    self.height += points / remove the word height
  }