# `impl-opaque`
[Documentation](https://docs.rs/impl-opaque/latest)
Declare struct fields and initializers in implementation area.
This macro tries to solve separation of field declarations, initializations and usages.
The `opaque` attribute generates struct declaration, struct constructor (`new` method) by collecting field declarations and initializers inside impl block.
This crate is no_std on runtime and requires alloc to build macro.
## Features
1. Declare fields inside method
```rust no_run
#[opaque]
impl Struct {
fn run(&mut self) {
#[field]
let ref mut count: i32 = 0;
*count += 1;
println!("{}", count);
}
}
```
2. Declare fields inside impl block
```rust no_run
#[opaque]
impl Struct {
field!(count: i32 = 0);
fn run(&mut self) {
self.count += 1;
println!("{}", self.count);
}
}
```
3. Convert constructor arguments into fields
```rust no_run
#[opaque(pub(self) count: i32)]
impl Struct {
fn run(&mut self) {
self.count += 1;
println!("{}", self.count);
}
}
```
4. Declare struct and implement trait at once
```rust no_run
#[opaque]
impl Iterator for Struct {
type Item = i32;
fn next(&mut self) -> Option<i32> {
#[field]
let ref mut count: i32 = 0;
*count += 1;
Some(*count)
}
}
```
5. Pattern matching and early return for fields inside a method
```rust no_run
#[opaque]
impl Struct {
pub fn run(&mut self) {
#[field]
let ref mut running @ true: bool = true else {
return
};
println!("run");
*running = false;
}
}
```
Attributes below `#[opaque]` will be moved to struct declaration.
Attributes below `#[field]` and `field!()` will be moved to field declaration.
Attribute reference
```rust no_run
#[opaque($(as $vis $(const)? ,)? $($($vis)? $ident: $ty),*)]
```
## Examples
See `examples` for simple example
## License
This crate is licensed under MIT OR Apache-2.0