Struct UseContext 

pub struct UseContext;

The UseContext pattern is used to define a trivial implementation of a provider trait, by forwarding the implementation to the consumer trait implementation of the context.

This pattern is the dual of the blanket implementation of a consumer trait, which forwards the implementation to its provider through the CgpProvider trait.

The main use case for UseContext is to be used as a higher-order provider in the argument to a different provider implementation. This decouples the dependencies between different CGP traits, and allows non-default providers to be used within another provider implementation.

For obvious reasons, UseContext should not be used as the delegation target from the context provider, as it would result in a cyclic dependency error.

The UseContext provider is automatically implemented for all CPG traits that are generated from #[cgp_component].

Example

Given the following component definition:

#[cgp_component(Greeter)]
pub trait CanGreet {
    fn greet(&self);
}

The following UseContext implementation would be generated:

impl<Context> Greeter<Context> for UseContext
where
    Context: CanGreet,
{
    fn greet(context: &Context) {
        context.greet()
    }
}