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<h1 align="center">Chain</h1>
<p align="center">
Mingling's Basic Components
</p>
---
## Intro
Like `Dispatcher`, `Chain` is also a core concept in building the entire **Mingling** framework. It is used to receive a dispatch of one type and convert it into another type.
```rust
dispatcher!("hello",
HelloCommand => HelloEntry);
// Define intermediate type ParsedHello, internally a String
pack!(ParsedHello = String);
// Define chain parse_hello (expands to ParseHello)
// Declare conversion from HelloEntry
#[chain]
fn parse_hello(prev: HelloEntry) -> NextProcess {
// Take the inner reference of HelloEntry
let args = &*prev;
// Extract the first argument, use default value "World"
// if it doesn't exist
let first = args.first().cloned().unwrap_or_else(|| "World".to_string());
// Pack the extracted argument into ParsedHello and
// dispatch to the next chain
ParsedHello::new(first).to_chain()
}
```
> **About NextProcess**
>
> `NextProcess` is a marker type in **Mingling**, from `mingling::marker`.
>
> It serves no functional purpose other than to simplify the declaration of chain functions. After the `chain!` macro expands, `NextProcess` will be replaced with `mingling::ChainProcess<ThisProgram>`.
## Manual Impl
You can also manually implement the basic `Chain` for finer control.
However, please note that within the `chain!` macro, a `register_type!` macro is executed. This macro does not expand to any content; it only informs the `gen_program` context that this type exists.
```rust
dispatcher!("hello",
HelloCommand => HelloEntry);
pack!(ParsedHello = String);
struct ParseHello;
impl Chain<ThisProgram> for ParseHello {
type Previous = HelloEntry;
fn proc(prev: Self::Previous)
-> ChainProcess<ThisProgram>
{
let args = &*prev;
let first = args
.first()
.cloned()
.unwrap_or_else(||
"World".to_string()
);
ParsedHello::new(first).to_chain()
}
}
// Register chain to the context
register_chain!(HelloEntry);
```
## 💡 Next Page
> **Basic Component** - Renderer [Go](./pages/2-basic/5-renderer)
|
