Trait MetaTuple 

pub unsafe trait MetaTuple: MetaAny {
    // Required methods
    fn get<T: 'static>(&self) -> Option<&T>;
    fn get_mut<T: 'static>(&mut self) -> Option<&mut T>;
    fn get_mut_ptr<T: 'static>(&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 { ... }
    fn join_dyn_ref(self, other: &dyn MetaAny) -> Join<Self, &DynMetaTuple>
       where Self: Sized { ... }
    fn join_dyn_mut(
        self,
        other: &mut dyn MetaAny,
    ) -> Join<Self, &mut DynMetaTuple>
       where Self: Sized { ... }
    fn query_ref<T: MetaQuery>(&self) -> Option<T::Output<'_>> { ... }
    fn query_mut<T: MetaQuery>(&mut self) -> Option<T::Output<'_>> { ... }
}

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.

Warning

Due to our semantics, for a tuple like (&A, A), get returns the first value while get_mut returns the second value, since &A cannot return a &mut A.

Dyn Compatibility

For a boxed dynamic version, see super trait MetaAny.

Safety

This trait cannot return overlapping references for different types.

For example

struct A{
    b: B,
    c: C,
}

The implementation can return A, or (B, C) but not both.

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.

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

Obtain a mutable item as pointer, 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.

fn join_dyn_ref(self, other: &dyn MetaAny) -> Join<Self, &DynMetaTuple>

where Self: Sized,

Join with a &dyn MetaAny.

fn join_dyn_mut(self, other: &mut dyn MetaAny) -> Join<Self, &mut DynMetaTuple>

where Self: Sized,

Join with a &mut dyn MetaAny.

fn query_ref<T: MetaQuery>(&self) -> Option<T::Output<'_>>

Try obtain multiple values from the MetaTuple.

fn query_mut<T: MetaQuery>(&mut self) -> Option<T::Output<'_>>

Try obtain multiple values from the 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>

fn get_mut_ptr<T: 'static>(&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>

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

impl<T: MetaTuple + ?Sized> MetaTuple for &T

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

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

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

impl<T: MetaTuple + ?Sized> MetaTuple for &mut T

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

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

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

Implementors

impl MetaTuple for DynMetaTuple

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

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