Does a `null` object has same memory footprint as ...

# random

[Ahmed]

Does a null object has same memory footprint as a non-null object?

var obj1: MyClass? = null
var obj2: MyClass = MyClass()

If we assume that with the members and methods MyClass is of 100 bytes.

Will obj1 also be of 100 bytes? Is there a recommended resource where I can learn more about this?

[Ahmed]

If obj1 is just a reference and points to null, holds no memory. Does this mean it’s true for member variables of MyClass as well i.e. the members that are currently null?

[Ahmed]

By no memory I mean the size of the reference which shall be 4 or 8 bytes depending on the system.

[Piotr Krzemiński]

In the first case, you don't construct the object so allocation doesn't happen. You wrote "null object" - it contradicts itself. It's just a nullable reference, set to null

[Ahmed]

Can same be said for the member variables of MyClass if they are set to null? e.g.

MyClass(myOtherClass = null)

[Piotr Krzemiński]

generally yes - myOtherClass just doesn't point at any object

[Piotr Krzemiński]

do you have an example case that says otherwise? or just asking out of curiosity?

[Ahmed]

Asking out of curiosity so I can engineer a little better. I am in the process of modelling a data class for different kind of listings. Initially I made 2 different models to keep the memory footprint low.

ListingModel and a DetailModel.

ListingModel is like a lite version of DetailModel.

With this new information what I can do is to make Detail a member of ListingModel which is initially set to null.

With this I will be able to share initial data that is already present and rest can be loaded later when a user navigates to Detail.

[krousseau]

My issue with objects where you intentionally leave a property null is usability. It becomes very difficult for consumers to know what is populated in a given scenario.

[Klitos Kyriacou]

Why not make DetailModel a subclass of ListingModel? Or make them both implement a Model interface?