- All Component references should be cached. The only other place where
GetComponentis allowed is just after instantiating a prefab and needing to set now appropriate values (since there is no other way). Always cache that
- Pre-cache everything, especially strings. Don't allocate at runtime if at all possible.
- Pool where appropriate.
- Be aware of performance costs of every move you make. I still use LINQ sometimes, and still write efficient code. If you're just starting out, prefix all your methods that are called from
Update_...you will quickly realize you're probably allocating in
- Have code on the same logical level, with clear separation of concerns. If your health script is setting the UI slider you're doing it wrong.
- Never swallow errors or pretend to handle them gracefully by avoiding affected code. If something is not assigned in the inspector, we want to know right away.
- Use events. Don't allow bi-directional
GetComponentlinks if possible, this is a sign Observer pattern is needed. If you don't know why you'd use events over a method call, you're doing it wrong. It's all about who knows about whom.
Conventions Of Practice:
- Singletons are a-OK. In general software development Singletons are regarded an anti-pattern but with careful analysis of pros and cons in game dev the conclusion is different. Even people are not able to manage themselves, they need managers. So objects need manager objects too. Further, in Unity all managers must be singletons, and self-instantiable ones. This means if the Singleton is not already in the scene, it will create itself with default values on first access. This is the only way to have self-contained prefabs, meaning if we put a prefab in any scene it will not cause
NullRefException, instead it will initialize all the required managers by accessing them. This way any prefab will run with realistic behavior even when thrown in an empty scene. This means we can't allow scene references on prefabs (see below).
- Scene-only object references on prefabs are not allowed. Scene object to scene object references also. This workflow will cause all kinds of grief, people do it for convenience and then they wonder why everything seems to be linked to everything else and why they have trouble when they duplicate the scene. Use a Registrator instead, if necessary. Registrator is GO that only stores references to scene-only objects in one place. Registrators are different in that they may not be actually present, so the component must be able to gracefully continue if so, with a message. Only ways of fetching data in an
MonoBehaviourfrom the other objects are:
GetComponentor references on the same prefab,
GetComponentor references on the same
GameObject, asking their self-instantiable manager classes or asking a Registrator. NOTE: You may argue that Registrators violate encapsulation. They do, but are worth it in practice.
- Never reference non-root go's of a prefab, instead use a Facade Pattern.
- Never set value to public fields in another class, that's unexpected (except for injection purposes). Calling methods is expected. No point in using
[SerializeField] privatesince the encapsulation is violated anyway by presence in Inspector.
Critique Of The Current Component System:
Startand other "magic methods" can be confusing. For example, enabling an object and accessing it's components right after it will not call
Start()before that, which now makes you access an object in a potentially invalid state. Instead, in these cases we use
OnEnable, however this messes up the assumed order of
Startif the object started disabled.
- Some magic methods are unexpected. For example,
Reset()is such a method. Instead, magic methods should be prefixed for convention.
- Relationships with Coroutines and enable/disable are strange.
- Physix collision rules are strange. Having a limiting amount of layers constrains the design space.
- Having only 1 tag per GO is weak, it would be better to have labels.
- Not having GOs without a Transform can cause performance penalties when we want organization.
OnTrigger...is quite weird from a design point of view. How do they know I want only 1 collider per object? Instead, those should be events of the Colliders components themselves that we subscribe to.
Misplaced Critiques Of The Current Component System:
Below is what I believe:
- Magic methods are not necessarily bad. They are a convention. Forcing an interface would be another convention that just forces an implementation on top of that.
- Having different
Awake()is not weird.
- "OOP code is hard to maintain" - No it isn't. It's so easy to reason about it's ridiculous. The fact most people write crappy code is not the point. They will write crappy code in any system, since they now have to worry about more things. There is a whole body of literature about how to write OOP code properly, and it's really not hard. So maybe instead of critiquing learning should be prescribed instead.