userdata parameter

Unity Engine
1

Hi, I would like to associate some user data with a GameObject, much like a void pointer so I can access it by

GameObject gameObject;
Someclass s = (Someclass)gameObject.userData;

2

You are more likely to get a response if you ask a question, but in this case I know what you are “asking.”

Without knowing the nature of Someclass, I have two suggestions.

  1. You can extend the GameObject class, and add a custom property, and use that.

  2. If Someclass is a component/script, you can use

gameObject.AddComponent(Someclass);
Someclass s = (Someclass) gameObject.GetComponent<Someclass>()
3

Typically you would use a component for this (see sccrstud92’s second example).

4

I’m not so sure about that, even if you can, there is no way of using it as all GameObjects use their base class.

This is the most viable case.

5

Sorry, I’m still new to Unity. I didn’t know you couldn’t extend GameObject like that and still use it like a GameObject. It’s what I would have done on a non-Unity application, so that’s why I suggested it.

6

I’m trying to avoid using GetComponent because it’s known to be slow. I’m hoping to make it a direct access like gameobject.transform, without the performance hit. Because it is a common component, I like to reduce memory instead of caching it per script.

7

Use GetComponent once at the beginning of the program, and store the reference into a property. Then, every time you need to access the component, just use the property instead of calling GetComponent.

8

This is what I’m trying to avoid. I have a few of these components, and they are common in many of the scripts, so I have to duplicate them in every script component, not to mention wasting memory since each script cache their local copy.

9

Give us more information on the nature of “Someclass,” and maybe we can give some more suggestions.

10

Wasting memory? its just a pointer !

Sometimes you need to waste memory to win performance.

11

There is

  • a generic data map which holds health, speed etc
  • a spatial partitioning component (I do additional processing for my 2d game)
  • a ai component
  • a behavior state component
  • a logic handler component

So the data map is used by most other scripts, same as partitioning scripts, and few others etc.

I’m expecting few hunderd of objects on screen, with 5 components each, on limited platforms, I would like to avoid memory, and reduce typing. Every startup calling GetComponent also increase loading time unnecessarily.

12

Limited platforms (iPhone?) can’t deal with that many on-screen objects in the first place, because of not having enough CPU + GPU power.

A desktop computer can do a million GetComponent calls in a fraction of a second. It’s “slow” only in comparison to direct access, which is why you would normally only bother to cache a GetComponent call if you’re doing it repeatedly. Even on an iPhone, a few hundred GetComponent calls isn’t going to take a perceivable amount of time. According to System.GC.GetTotalMemory, 1000 GetComponent references uses about 4KB…not exactly an amount to worry about even on limited platforms. It doesn’t store a copy of the script, if that’s what you’re thinking. As AzulValium said, it’s just a pointer.

–Eric