The function takes the 3 parameters described above into this function gamemanager. Createentity(string prefabname, vector3 position, quaternion rotation). If there was an error spawning the entity or an invalid prefab name was supplied the entity will be null. We should check for this before calling the spawn() function or we risk throwing an error. Represents the interface for a generic entity whose fields and edges can be accessed by str name regardless of compile-time characteristics. Represents a builder interface for some ent, capable of building a new ent instance and also saving the new ent to the database at the same time.
Name resolution is the compile-time process of tying paths, identifiers, and labels to entity declarations. Entities that explicitly introduce a name in the source code are items lets expand the idea of an entity a little more. It is only an id, this means that when creating your entities, you can just use an increasing integer counter. But how do you use that id and what is its relationship to a component? Okay, now lets pretend we have two components defined position and velocity, the key parts of movement in xyz game. You will have multiple entities using these two components, so some form of storage is needed, such as an array per component.
This chapter will introduce the entire of an entity component system (ecs), which will form the backbone of the rest of this tutorial. Rust has a very good ecs, called specs - and this tutorial will show you how to use it, and try to demonstrate some of the early benefits of using it. If youve worked on games before, you may well be used to an object oriented design (this is very common, even in the original python libtcod tutorial that inspired this one). Bevy is a game engine written in rust that is known for featuring a very ergonomic entity component system. In the ecs pattern, entities are unique things that are made up of components, like objects in a game world.
What makes bevys api so elegant is that users can write regular functions in rust, and bevy will know how to call them by their type signature, dispatching the correct data. In rust, access to mutable state is very controlled only one mutable reference to an object can exist at a time. One approach is to use interior mutability, typically rcrefcellt as a reference to an object, which can be shared widely. When code needs to mutate state, it borrows a mutable reference, does the mutation, then promptly releases the borrow. .