Trait WriteState

pub trait WriteState: ReadState {
    // Required method
    fn write<'life0, 'async_trait, T>(
        &'life0 self,
        op: impl 'async_trait + Send + for<'a> FnOnce(&'a mut Self::State) -> BoxFuture<'a, T>,
    ) -> Pin<Box<dyn Future<Output = T> + Send + 'async_trait>>
       where T: 'async_trait,
             Self: 'async_trait,
             'life0: 'async_trait;
}

A state which allows exclusive, write access.

Required Methods

fn write<'life0, 'async_trait, T>( &'life0 self, op: impl 'async_trait + Send + for<'a> FnOnce(&'a mut Self::State) -> BoxFuture<'a, T>, ) -> Pin<Box<dyn Future<Output = T> + Send + 'async_trait>>

where T: 'async_trait, Self: 'async_trait, 'life0: 'async_trait,

Do an operation with mutable access to the state.

Limitations

The reason this function takes a visitor function to apply to the state, rather than just returning a mutable reference to the state, is to allow implementations that cannot provide a plain mutable reference directly. For example, [RwLock] can produce a smart reference, a RwLockWriteGuard, but not a plain mutable reference.

Note that GATs may allow us to make this interface more ergonomic in the future. With stable GATs, this trait could be written like

trait WriteState {
    type State: 'static;
    type MutReference<'a>: 'a + DerefMut<Target = Self::State>;
    fn write(&self) -> Self::MutReference<'_>;
}

Like many function parameters in tide_disco, the function to apply to the state is also required to return a boxed future.

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 WriteState for ()

This allows you to do api.post(...) in a simple API where the state is ().

fn write<'life0, 'async_trait, T>( &'life0 self, op: impl 'async_trait + Send + for<'a> FnOnce(&'a mut Self::State) -> BoxFuture<'a, T>, ) -> Pin<Box<dyn Future<Output = T> + Send + 'async_trait>>

where T: 'async_trait, Self: 'async_trait, 'life0: 'async_trait,

impl<State: 'static + Send + Sync> WriteState for Mutex<State>

fn write<'life0, 'async_trait, T>( &'life0 self, op: impl 'async_trait + Send + for<'a> FnOnce(&'a mut Self::State) -> BoxFuture<'a, T>, ) -> Pin<Box<dyn Future<Output = T> + Send + 'async_trait>>

where T: 'async_trait, Self: 'async_trait, 'life0: 'async_trait,

impl<State: 'static + Send + Sync> WriteState for RwLock<State>

fn write<'life0, 'async_trait, T>( &'life0 self, op: impl 'async_trait + Send + for<'a> FnOnce(&'a mut Self::State) -> BoxFuture<'a, T>, ) -> Pin<Box<dyn Future<Output = T> + Send + 'async_trait>>

where T: 'async_trait, Self: 'async_trait, 'life0: 'async_trait,

impl<W: Send + Sync + WriteState> WriteState for Arc<W>

fn write<'life0, 'async_trait, T>( &'life0 self, op: impl 'async_trait + Send + for<'a> FnOnce(&'a mut Self::State) -> BoxFuture<'a, T>, ) -> Pin<Box<dyn Future<Output = T> + Send + 'async_trait>>

where T: 'async_trait, Self: 'async_trait, 'life0: 'async_trait,

Implementors