This crate allows the user to represent state in the database using Rust enums. This is achieved
through a proc macro. First the macro looks at your chosen sql_type, and then it devises a
corresponding Rust type. The mapping is as follows:
| SQL | Rust |
|--|--|
| SmallInt | i16 |
| Integer | i32 |
| Int | i32 |
| BigInt | i64 |
| VarChar | String |
| Text | String |
The macro then generates three impls: a FromSql impl, an ToSql impl and a
TryFrom impl, which allow conversion between the Sql type an the enum (FromSql and ToSql),
and from the Rust type into the enum (TryInto).
```rust
use dieselenum::DbEnum; use diesel::sqltypes::SmallInt;
pub struct CustomError { msg: String, status: u16, }
impl CustomError { fn not_found(msg: String) -> Self { Self { msg, status: 404, } } }
pub enum Status {
/// Will be represented as 0.
Ready,
/// Will be represented as 1.
Pending,
}
Alternatively you can use strings, with will be cast to lowercase. (e.g. `Status::Ready` will be
stored as `"ready"` in the database):
rust
pub enum Status {
/// Will be represented as "ready".
Ready,
/// Will be represented as "pending".
Pending,
}
Another option is to manually override the values set for each or some of the variants. This is done
using the `val` attribute:
rust
pub enum Status {
/// Will be represented as "reddy".
#[val = "reddy"]
Ready,
/// Will be represented as "pending".
Pending,
}
```