cgp_component/types/
use_context.rs

1use crate::WithProvider;
2
3/**
4    The `UseContext` pattern is used to define a trivial implementation of
5    a provider trait, by forwarding the implementation to the consumer trait
6    implementation of the context.
7
8    This pattern is the _dual_ of the blanket implementation of a consumer trait,
9    which forwards the implementation to its provider through the `CgpProvider` trait.
10
11    The main use case for `UseContext` is to be used as a _higher-order provider_
12    in the argument to a different provider implementation. This decouples the
13    dependencies between different CGP traits, and allows non-default providers
14    to be used within another provider implementation.
15
16    For obvious reasons, `UseContext` should not be used as the delegation target
17    from the context provider, as it would result in a cyclic dependency error.
18
19    The `UseContext` provider is automatically implemented for all CPG traits that
20    are generated from `#[cgp_component]`.
21
22    ## Example
23
24    Given the following component definition:
25
26    ```rust,ignore
27    #[cgp_component(Greeter)]
28    pub trait CanGreet {
29        fn greet(&self);
30    }
31    ```
32
33    The following `UseContext` implementation would be generated:
34
35    ```rust,ignore
36    impl<Context> Greeter<Context> for UseContext
37    where
38        Context: CanGreet,
39    {
40        fn greet(context: &Context) {
41            context.greet()
42        }
43    }
44    ```
45*/
46pub struct UseContext;
47
48pub type WithContext = WithProvider<UseContext>;
cgp_component/types/use_context.rs

cgp_component/types/
use_context.rs
