Trait ComponentMutability

pub trait ComponentMutability: Seal + 'static {
    const MUTABLE: bool;
}

The mutability option for a Component. This can either be:

• Mutable
• Immutable

This is controlled through either Component::Mutability or #[component(immutable)] when using the derive macro.

Immutable components are guaranteed to never have an exclusive reference, &mut ..., created while inserted onto an entity. In all other ways, they are identical to mutable components. This restriction allows hooks to observe all changes made to an immutable component, effectively turning the OnInsert and OnReplace hooks into a OnMutate hook. This is not practical for mutable components, as the runtime cost of invoking a hook for every exclusive reference created would be far too high.

Examples

#[derive(Component)]
#[component(immutable)]
struct ImmutableFoo;

Required Associated Constants

const MUTABLE: bool

Boolean to indicate if this mutability setting implies a mutable or immutable component.

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementors

impl ComponentMutability for Immutable

const MUTABLE: bool = false

impl ComponentMutability for Mutable

const MUTABLE: bool = true