111 lines
3.6 KiB
Markdown
111 lines
3.6 KiB
Markdown
Convert number to enum
|
|
======================
|
|
|
|
[<img alt="github" src="https://img.shields.io/badge/github-dtolnay/enumn-8da0cb?style=for-the-badge&labelColor=555555&logo=github" height="20">](https://github.com/dtolnay/enumn)
|
|
[<img alt="crates.io" src="https://img.shields.io/crates/v/enumn.svg?style=for-the-badge&color=fc8d62&logo=rust" height="20">](https://crates.io/crates/enumn)
|
|
[<img alt="docs.rs" src="https://img.shields.io/badge/docs.rs-enumn-66c2a5?style=for-the-badge&labelColor=555555&logoColor=white&logo=data:image/svg+xml;base64,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" height="20">](https://docs.rs/enumn)
|
|
[<img alt="build status" src="https://img.shields.io/github/workflow/status/dtolnay/enumn/CI/master?style=for-the-badge" height="20">](https://github.com/dtolnay/enumn/actions?query=branch%3Amaster)
|
|
|
|
This crate provides a derive macro to generate a function for converting a
|
|
primitive integer into the corresponding variant of an enum.
|
|
|
|
The generated function is named `n` and has the following signature:
|
|
|
|
```rust
|
|
impl YourEnum {
|
|
pub fn n(value: Repr) -> Option<Self>;
|
|
}
|
|
```
|
|
|
|
where `Repr` is an integer type of the right size as described in more
|
|
detail below.
|
|
|
|
## Example
|
|
|
|
```rust
|
|
use enumn::N;
|
|
|
|
#[derive(PartialEq, Debug, N)]
|
|
enum Status {
|
|
LegendaryTriumph,
|
|
QualifiedSuccess,
|
|
FortuitousRevival,
|
|
IndeterminateStalemate,
|
|
RecoverableSetback,
|
|
DireMisadventure,
|
|
AbjectFailure,
|
|
}
|
|
|
|
fn main() {
|
|
let s = Status::n(1);
|
|
assert_eq!(s, Some(Status::QualifiedSuccess));
|
|
|
|
let s = Status::n(9);
|
|
assert_eq!(s, None);
|
|
}
|
|
```
|
|
|
|
## Signature
|
|
|
|
The generated signature depends on whether the enum has a `#[repr(..)]`
|
|
attribute. If a `repr` is specified, the input to `n` will be required to be
|
|
of that type.
|
|
|
|
```rust
|
|
#[derive(enumn::N)]
|
|
#[repr(u8)]
|
|
enum E {
|
|
/* ... */
|
|
}
|
|
|
|
// expands to:
|
|
impl E {
|
|
pub fn n(value: u8) -> Option<Self> {
|
|
/* ... */
|
|
}
|
|
}
|
|
```
|
|
|
|
On the other hand if no `repr` is specified then we get a signature that is
|
|
generic over a variety of possible types.
|
|
|
|
```rust
|
|
impl E {
|
|
pub fn n<REPR: Into<i64>>(value: REPR) -> Option<Self> {
|
|
/* ... */
|
|
}
|
|
}
|
|
```
|
|
|
|
## Discriminants
|
|
|
|
The conversion respects explictly specified enum discriminants. Consider
|
|
this enum:
|
|
|
|
```rust
|
|
#[derive(enumn::N)]
|
|
enum Letter {
|
|
A = 65,
|
|
B = 66,
|
|
}
|
|
```
|
|
|
|
Here `Letter::n(65)` would return `Some(Letter::A)`.
|
|
|
|
<br>
|
|
|
|
#### License
|
|
|
|
<sup>
|
|
Licensed under either of <a href="LICENSE-APACHE">Apache License, Version
|
|
2.0</a> or <a href="LICENSE-MIT">MIT license</a> at your option.
|
|
</sup>
|
|
|
|
<br>
|
|
|
|
<sub>
|
|
Unless you explicitly state otherwise, any contribution intentionally submitted
|
|
for inclusion in this crate by you, as defined in the Apache-2.0 license, shall
|
|
be dual licensed as above, without any additional terms or conditions.
|
|
</sub>
|