Trait MetaTuple

pub trait MetaTuple: MetaBox {
    // Required methods
    fn get<T: 'static>(&self) -> Option<&T>;
    fn get_mut<T: 'static>(&mut self) -> Option<&mut T>;

    // Provided methods
    fn join<T: 'static>(self, other: T) -> Join<Self, MetaItem<T>>
       where Self: Sized { ... }
    fn join_ref<T: 'static>(self, other: &T) -> Join<Self, &MetaItem<T>>
       where Self: Sized { ... }
    fn join_mut<T: 'static>(self, other: &mut T) -> Join<Self, &mut MetaItem<T>>
       where Self: Sized { ... }
    fn join_tuple<T: MetaTuple>(self, other: T) -> Join<Self, T>
       where Self: Sized { ... }
}

A statically typed opaque tuple that can contain any type.

This is a zero cost abstraction in most cases. To create, see macro meta_tuple!.

Use Case

This trait is generally used for complicated input and output abstractions, for example

pub trait CardComponent {
    fn play(&self, input: &impl MetaTuple) -> impl MetaTuple;
}

impl CardComponent for Attack {
    fn play(&self, input: &impl MetaTuple) -> impl MetaTuple {
        let attacker = input.get::<Attacker>().unwrap();
        let defender = input.get::<Defender>().unwrap();
        let damage_dealt = self.calculate_damage(attacker, defender);
        input.join(DamageDealt(damage_dealt))
    }
}

pub trait CardComponent {
    pub fn play(&self, input: &impl MetaTuple) -> impl MetaTuple;
}

Semantics

For functions like get, we look for the first correct item, duplicated items will not be used.

&impl MetaTuple and &mut impl MetaTuple both implement MetaTuple, for a tuple like (&A, A), get returns the first value while get_mut returns the second value.

Dyn Compatibility

For a boxed dynamic version, see super trait MetaBox.

Required Methods

fn get<T: 'static>(&self) -> Option<&T>

Obtain an item, if exists.

fn get_mut<T: 'static>(&mut self) -> Option<&mut T>

Obtain a mutable item, if exists.

Provided Methods

fn join<T: 'static>(self, other: T) -> Join<Self, MetaItem<T>>

where Self: Sized,

Join with another concrete value.

fn join_ref<T: 'static>(self, other: &T) -> Join<Self, &MetaItem<T>>

where Self: Sized,

Join with a reference to a concrete value.

If querying for a mutable reference, will return None.

fn join_mut<T: 'static>(self, other: &mut T) -> Join<Self, &mut MetaItem<T>>

where Self: Sized,

Join with a mutable reference to a concrete value.

fn join_tuple<T: MetaTuple>(self, other: T) -> Join<Self, T>

where Self: Sized,

Join with another MetaTuple.

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.

Implementations on Foreign Types

impl MetaTuple for ()

fn get<T: 'static>(&self) -> Option<&T>

fn get_mut<T: 'static>(&mut self) -> Option<&mut T>

impl<T: 'static> MetaTuple for Option<T>

fn get<U: 'static>(&self) -> Option<&U>

fn get_mut<U: 'static>(&mut self) -> Option<&mut U>

impl<T: MetaTuple> MetaTuple for &T

fn get<U: 'static>(&self) -> Option<&U>

fn get_mut<U: 'static>(&mut self) -> Option<&mut U>

impl<T: MetaTuple> MetaTuple for &mut T

fn get<U: 'static>(&self) -> Option<&U>

fn get_mut<U: 'static>(&mut self) -> Option<&mut U>

Implementors

impl<A: MetaTuple, B: MetaTuple> MetaTuple for Join<A, B>

impl<T: 'static> MetaTuple for MetaItem<T>