Struct ChangeTracker

pub struct ChangeTracker<T>
where
    T: Component,
{ /* private fields */ }

Helper to track changes in T components

For each entity with a T component, a private component is inserted which stores the value as of the most recent call to track. This provides robust, exact change detection at the cost of visiting each possibly-changed entity. It is a good fit for entities that will typically be visited regardless, and components having fast Clone and PartialEq impls. For components which are expensive to compare and/or clone, consider instead tracking changes manually, e.g. by setting a flag in the component’s DerefMut implementation.

Always use exactly one ChangeTracker per World per component type of interest. Using multiple trackers of the same T on the same world, or using the same tracker across multiple worlds, will produce unpredictable results.

Implementations

impl<T> ChangeTracker<T>

where T: Component,

pub fn new() -> ChangeTracker<T>

Create a change tracker for T components

pub fn track<'a>(&'a mut self, world: &'a mut World) -> Changes<'a, T>

where T: Clone + PartialEq,

Determine the changes in T components in world since the previous call

Trait Implementations

impl<T> Default for ChangeTracker<T>

where T: Component,

fn default() -> ChangeTracker<T>

Returns the “default value” for a type.