MessageCursor

Struct MessageCursor 

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pub struct MessageCursor<E>
where E: Message,
{ /* private fields */ }
Expand description

Stores the state for a MessageReader or MessageMutator.

Access to the Messages<E> resource is required to read any incoming messages.

In almost all cases, you should just use a MessageReader or MessageMutator, which will automatically manage the state for you.

However, this type can be useful if you need to manually track messages, such as when you’re attempting to send and receive messages of the same type in the same system.

§Example

use bevy_ecs::prelude::*;
use bevy_ecs::message::{Message, MessageCursor};

#[derive(Message, Clone, Debug)]
struct MyMessage;

/// A system that both sends and receives messages using a [`Local`] [`MessageCursor`].
fn send_and_receive_messages(
    // The `Local` `SystemParam` stores state inside the system itself, rather than in the world.
    // `MessageCursor<T>` is the internal state of `MessageMutator<T>`, which tracks which messages have been seen.
    mut local_message_reader: Local<MessageCursor<MyMessage>>,
    // We can access the `Messages` resource mutably, allowing us to both read and write its contents.
    mut messages: ResMut<Messages<MyMessage>>,
) {
    // We must collect the messages to resend, because we can't mutate messages while we're iterating over the messages.
    let mut messages_to_resend = Vec::new();

    for message in local_message_reader.read(&mut messages) {
         messages_to_resend.push(message.clone());
    }

    for message in messages_to_resend {
        messages.write(MyMessage);
    }
}

Implementations§

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impl<E> MessageCursor<E>
where E: Message,

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pub fn read<'a>( &'a mut self, messages: &'a Messages<E>, ) -> MessageIterator<'a, E>

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pub fn read_mut<'a>( &'a mut self, messages: &'a mut Messages<E>, ) -> MessageMutIterator<'a, E>

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pub fn read_with_id<'a>( &'a mut self, messages: &'a Messages<E>, ) -> MessageIteratorWithId<'a, E>

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pub fn read_mut_with_id<'a>( &'a mut self, messages: &'a mut Messages<E>, ) -> MessageMutIteratorWithId<'a, E>

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pub fn par_read<'a>( &'a mut self, messages: &'a Messages<E>, ) -> MessageParIter<'a, E>

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pub fn par_read_mut<'a>( &'a mut self, messages: &'a mut Messages<E>, ) -> MessageMutParIter<'a, E>

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pub fn len(&self, messages: &Messages<E>) -> usize

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pub fn missed_messages(&self, messages: &Messages<E>) -> usize

Amount of messages we missed.

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pub fn is_empty(&self, messages: &Messages<E>) -> bool

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pub fn clear(&mut self, messages: &Messages<E>)

Trait Implementations§

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impl<E> Clone for MessageCursor<E>
where E: Message,

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fn clone(&self) -> MessageCursor<E>

Returns a duplicate of the value. Read more
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fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl<E> Debug for MessageCursor<E>
where E: Debug + Message,

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fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter. Read more
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impl<E> Default for MessageCursor<E>
where E: Message,

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fn default() -> MessageCursor<E>

Returns the “default value” for a type. Read more

Auto Trait Implementations§

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impl<E> Freeze for MessageCursor<E>

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impl<E> RefUnwindSafe for MessageCursor<E>
where E: RefUnwindSafe,

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impl<E> Send for MessageCursor<E>

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impl<E> Sync for MessageCursor<E>

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impl<E> Unpin for MessageCursor<E>
where E: Unpin,

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impl<E> UnwindSafe for MessageCursor<E>
where E: UnwindSafe,

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impl<T> Any for T
where T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T, U> AsBindGroupShaderType<U> for T
where U: ShaderType, &'a T: for<'a> Into<U>,

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fn as_bind_group_shader_type(&self, _images: &RenderAssets<GpuImage>) -> U

Return the T ShaderType for self. When used in AsBindGroup derives, it is safe to assume that all images in self exist.
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> CloneToUninit for T
where T: Clone,

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unsafe fn clone_to_uninit(&self, dest: *mut u8)

🔬This is a nightly-only experimental API. (clone_to_uninit)
Performs copy-assignment from self to dest. Read more
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impl<T> Downcast for T
where T: Any,

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fn into_any(self: Box<T>) -> Box<dyn Any>

Converts Box<dyn Trait> (where Trait: Downcast) to Box<dyn Any>, which can then be downcast into Box<dyn ConcreteType> where ConcreteType implements Trait.
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fn into_any_rc(self: Rc<T>) -> Rc<dyn Any>

Converts Rc<Trait> (where Trait: Downcast) to Rc<Any>, which can then be further downcast into Rc<ConcreteType> where ConcreteType implements Trait.
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fn as_any(&self) -> &(dyn Any + 'static)

Converts &Trait (where Trait: Downcast) to &Any. This is needed since Rust cannot generate &Any’s vtable from &Trait’s.
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fn as_any_mut(&mut self) -> &mut (dyn Any + 'static)

Converts &mut Trait (where Trait: Downcast) to &Any. This is needed since Rust cannot generate &mut Any’s vtable from &mut Trait’s.
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impl<T> Downcast for T
where T: Any,

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fn into_any(self: Box<T>) -> Box<dyn Any>

Convert Box<dyn Trait> (where Trait: Downcast) to Box<dyn Any>. Box<dyn Any> can then be further downcast into Box<ConcreteType> where ConcreteType implements Trait.
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fn into_any_rc(self: Rc<T>) -> Rc<dyn Any>

Convert Rc<Trait> (where Trait: Downcast) to Rc<Any>. Rc<Any> can then be further downcast into Rc<ConcreteType> where ConcreteType implements Trait.
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fn as_any(&self) -> &(dyn Any + 'static)

Convert &Trait (where Trait: Downcast) to &Any. This is needed since Rust cannot generate &Any’s vtable from &Trait’s.
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fn as_any_mut(&mut self) -> &mut (dyn Any + 'static)

Convert &mut Trait (where Trait: Downcast) to &Any. This is needed since Rust cannot generate &mut Any’s vtable from &mut Trait’s.
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impl<T> DowncastSend for T
where T: Any + Send,

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fn into_any_send(self: Box<T>) -> Box<dyn Any + Send>

Converts Box<Trait> (where Trait: DowncastSend) to Box<dyn Any + Send>, which can then be downcast into Box<ConcreteType> where ConcreteType implements Trait.
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impl<T> DowncastSync for T
where T: Any + Send + Sync,

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Convert Arc<Trait> (where Trait: Downcast) to Arc<Any>. Arc<Any> can then be further downcast into Arc<ConcreteType> where ConcreteType implements Trait.
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fn from(t: T) -> T

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Creates Self using default().

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const WITNESS: W = W::MAKE

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const TYPE_EQ: TypeEq<T, <T as Identity>::Type> = TypeEq::NEW

Proof that Self is the same type as Self::Type, provides methods for casting between Self and Self::Type.
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type Type = T

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Calls U::from(self).

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fn into_result(self) -> Result<T, RunSystemError>

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fn is<T>() -> bool
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type Owned = T

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Performs the conversion.
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where S: Into<Dispatch>,

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