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iOS Object-Oriented Swift 2.0 Complex Data Structures Initializers and Self

zaid
zaid
1,806 Points
Posted by zaid
zaid
1,806 Points

Which side of the operator is referring to the global and which side is referring to the local constant

struct Point { let x: Int let y: Int

init(x: Int, y: Int) {
    self.x = x // Does the left side of the operation reference the global or the local constant?
    self.y = y
}

Does it matter which side the constant is at all? Does self. will always refer to global?

2 Answers

Abdullah Althobetey
Abdullah Althobetey
18,216 Points
Abdullah Althobetey
Abdullah Althobetey
18,216 Points

self.x refers to the x property of the object itself. Where x refers to the argument x of the function. We use self.x = x just to distinguish between the x, the property, and the x, the argument. if the argument were named something else other than x (for example xCord), then we do not need to write self.x because in this case we only have one x which is the property x

init(xCord: Int, yCord: Int) {
    x = xCord
    y = yCord
}

Hope this help.

Damien Watson
Damien Watson
27,419 Points
Damien Watson
Damien Watson
27,419 Points

Always learning, cheers. :)

Damien Watson
Damien Watson
27,419 Points
Damien Watson
Damien Watson
27,419 Points

Hi, its not so much which side, but what you are setting on left or right.

In your example, the left, the 'self' denotes the object you are setting (global for your object) and the right side it what you are setting it to.

I've changed the variable names purely to make it more descriptive (this is not required or necessarily recommended):

init(updateToX: Int, updateToY: Int) {
    self.x = updateToX
    self.y = updateToY
}
zaid
zaid
1,806 Points
zaid
zaid
1,806 Points

This might be a big questions, but I can't wrap my head around the purpose of using init every. Why not just let Xcode handle it?

Damien Watson
Damien Watson
27,419 Points
Damien Watson
Damien Watson
27,419 Points

It depends if the class you're using has it set up the way you need to use it. If the default setting is as required then sure, leave xCode to handle it as per default initialise method.

If you need to customise it in any way or it is a brand new class, then you need to write your own init method. In the case of a new class, xCode doesn't know how to handle it yet as it didn't exist until now. 'init' is the constructor method, tells the class how to build the default instance.

Does this make sense?