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iOS Object-Oriented Swift 2.0 Classes Instances of Classes

Posted by Carl Smith
Carl Smith
8,185 Points

Not sure how to create and instance and assign to someShape

Confused on what this means.

classes.swift 
// Enter your code below
class Shape{
    var numberOfSides: Int

    init(numberOfSides: Int){
        self.numberOfSides = someShape
    }
}

2 Answers

jcorum
jcorum
71,830 Points

There was a slight problem in your initializer:

class Shape{
    var numberOfSides: Int

    init(numberOfSides: Int){
        self.numberOfSides = numberOfSides
    }
}
let someShape = Shape(numberOfSides: 6)

When the initializer is called you will send it an int (say 6). The initializer takes that value and assigns it to its stored property with this statement: self.numberOfSides = numberOfSides

What it's saying is: assign to my stored property named numberOfSides (self.numberOfSides) the value passed in by the parameter numberOfSides.

Then, once the class is fixed up, you can create a Shape object named someShape by calling the initializer with an int value. Don't forget that you have to provide the name of the parameter as well as the value.

Carl Smith
Carl Smith
8,185 Points

I'm still a little foggy on the initializer, I know how to write it, just not sure what it's purpose is. I'll watch the video again and hopefully get more familiar with it.

jcorum
jcorum
71,830 Points
jcorum
jcorum
71,830 Points

The purpose of the initializer is to (1) create an object from the class, and (2) before doing so to make sure every stored property of the class has a value before the object is created. In this case it is to make sure every Shape object has its number of sides specified. Or, in other words, to make sure the stored property numberOfSides has an int value.

Since the initializer takes an int you cannot do this:

let someShape = Shape()

or this:

let someShape = Shape(numberOfSides: "3")

If the Shape class had two stored properties: numberOfSides and color, then the constructor would look like this:

``swift init(numberOfSides: Int, color: String){ self.numberOfSides = numberOfSides self.color = color }

and you would create Shape objects like this:

```swift
let someShape = Shape(numberOfSides: 6, color: "red")