CODEWITHSUNDEEP
c#parent-childrelationship
Biene Maja
Biene Maja

Reputation: 181

Best way to access parent properties from a child class

i'm working on a tile editor. In the editor you can load a tile map. Each tile map can have multiple layers. A tile map has a list of it's layers. I now need tile map properties in the layer class (things like tile width/height e.g.). I'm now asking myself what is the best way to do this.

  1. I could make a bidirectional relationship by introducing a tilemap property in the layer class, so that i have access to everything i need from there. But then i would have to take care of two sides of the relationship.

  2. I could give all the needed properties to the layer class with the constructor, but then they basicly become layer properties (aka they are different objects for every layer).

  3. Same as 2 but give the properties to the layer with "ref" paramter.

  4. I could make a class called something like TileMapLayerProperties where i put all the properties in and then pass the object to the layer classes. Advantage would be that all the properties would be the same and only the tileMapLayerProperties-reference would be per instance. Another advantage would be the "definition" of the layer constructor becoming much shorter.

So any suggestions / tips would be appreciated.

Upvotes: 0

Views: 2649

Answers (3)

Sebastian Negraszus
Sebastian Negraszus

Reputation: 12195

A bi-directional association (1) might be OK or not, depending on what properties and methods a tile map contains and what a layer should be able to know and access. If a tile map has a DeleteAllLayers method and layers should not be able to call it, then layers cannot have direct access to their parent.

Creating a dedicated property object (4) seems more clean to me. That way you have one object with all necessary information that you can pass around, but it does not contain more than that, especially it does not allow calling destructive methods etc.

Passing the properties to the constructor (2) is similar to (4), but more verbose and less object-oriented. It's fine when you have 1 or 2 properties, but with more than a few it gets ugly and unmaintainable.

But there is another problem: If the properties are of immutable types (e.g. int, string), then the layers do not see changes made in the map. They only see their private copy!

I don't understand (3). How does the ref keyword change (2)? It only allows the callee to change the value of a variable passed by the caller. Or do you mean objects with reference types?

Another solution

Interfaces would be another way to solve this. You could create a ITileMapLayerProperties interface that provides all the properties and pass it to the layer's constructor. The map could either implement the interface itself or contain a TileMapLayerProperties object that implements the interface. But the layer does not need to know this.

Upvotes: 1

Shaharyar
Shaharyar

Reputation: 12439

I think option is 3 is better. You can pass a reference of your ParentClass to the ChildClass and can have directly access to all public properties. I suggested it better because what ever changes you will make whether from ChildClass or ParentClass, all other layers will inherit those changes.

Upvotes: 0

Th3BFG
Th3BFG

Reputation: 315

Option 2 would work for what you are trying to do, and you may not need to include the 'ref' keyword. I'm curious, what kind of datamembers are you trying to access from the child classes? If they are collections then you may not need the 'ref' keyword. Another option would be to make the parent class static, but I'm not sure if this is the outcome you're looking for. Can you load more than one tile map at a time? If not, consider the static class option.

Upvotes: 0

Related Questions