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iOS Object-Oriented Swift Inheritance Overriding Methods

Posted by swiftdev
swiftdev
3,655 Points

Help me with the "override" thing!

So I'm on this challenge and I really don't know or understand what I'm doing. I watched the video again, but I still don't understand what "override" does. Also while I'm trying to type things into playground and error keeps popping up that says "Consecutive declarations on a line must be separated by ';'" or "Expected declaration". I'm not trying to put any commands on the same line and I don't know why it's expecting another declaration. Can somebody help me with both of these?!

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){
        width += points
        height += points
    }
}

class RoundButton: Button {
    var cornerRadius: Double = 5.0
    override func incrementBy(points: Double = 7.0){
        width += points
        height += points

}

1 Answer

jcorum
jcorum
71,830 Points

This is a bit tricky. First, you are missing a closing curly brace at the end of your function. When that is fixed the compiler error is this:

swift_lint.swift:21:17: error: argument names for method 'incrementBy(points:)' do not match those of overridden method 'incrementBy'
  override func incrementBy(points: Double = 7.0){

Yes, the documentation says default values can be done the way, you are doing it, but not when overriding. As the error message say, when overriding the argument names must be the same. What you need is this:

    override func incrementBy(points: Double) {
        width += 7.0
        height += 7.0
    }

What override does is create a function in a subclass with the same name and method signature (number and type of arguments or parameters) and a different code block. Actually, the code could be the same but then there would be little reason to do the override.

swiftdev
swiftdev
3,655 Points

Thank you! I get it now.