Trait TryNextWithContext 

pub trait TryNextWithContext {
    type Item;
    type Error;
    type Context;

    // Required method
    fn try_next_with_context(
        &mut self,
        context: &mut Self::Context,
    ) -> Result<Option<Self::Item>, Self::Error>;

    // Provided method
    fn try_collect_with_context(
        &mut self,
        context: &mut Self::Context,
    ) -> Result<Vec<Self::Item>, Self::Error> { ... }
}

Context-aware, fallible producer.

A trait for types that can produce items one at a time with the help of an external context, where fetching the next item may fail.

This trait is synchronous — each call to try_next blocks until an item is produced or an error occurs.

The Context type allows the caller to provide additional state or resources used during iteration. It can hold shared mutable state, configuration data, or external resources such as file handles, buffers, or network clients. Each call to try_next receives a mutable reference to this context.

See the module-level documentation for details and examples.

Required Associated Types

type Item

The type of items yielded by this source.

type Error

The error type that may be returned when producing the next item fails.

type Context

The type of context passed to each call to try_next.

Required Methods

fn try_next_with_context( &mut self, context: &mut Self::Context, ) -> Result<Option<Self::Item>, Self::Error>

Attempts to produce the next item, using the provided mutable context.

Returns:

• Ok(Some(item)) — a new item was produced,
• Ok(None) — the source is exhausted,
• Err(e) — iteration failed with an error.

Provided Methods

fn try_collect_with_context( &mut self, context: &mut Self::Context, ) -> Result<Vec<Self::Item>, Self::Error>

Collects all remaining items into a Vec, using the given context.

The method repeatedly calls try_next_with_context until None or an error is returned, collecting all successful items into a vector. If any call returns Err(e), iteration stops immediately and that error is returned.

Feature

This method is only available when the alloc feature is enabled.

Implementors