nulid_derive

Derive macros for types that wrap Nulid.

This crate provides procedural macros to automatically implement common traits for newtype wrappers around Nulid, eliminating boilerplate code.

Features

The Id derive macro automatically implements:

TryFrom<String> - Parse from owned String
TryFrom<&str> - Parse from string slice
From<Nulid> - Create wrapper from Nulid
From<WrapperType> for Nulid - Extract inner Nulid
AsRef<Nulid> - Borrow inner Nulid
std::fmt::Display - Format as Base32 string
std::fmt::Debug - Debug formatting
std::str::FromStr - Parse from string using .parse()
Copy - Value semantics (automatically provides Clone)
PartialEq and Eq - Equality comparison with other wrappers
PartialEq<Nulid> - Direct equality comparison with Nulid
PartialOrd and Ord - Ordering comparison with other wrappers
PartialOrd<Nulid> - Direct ordering comparison with Nulid
Hash - Hashing support for collections

Usage

Add this to your Cargo.toml:

[dependencies]
nulid = { version = "0.5", features = ["derive"] }

Then use the derive macro on your wrapper types:

use nulid::{Nulid, Id};

#[derive(Id)]
pub struct UserId(Nulid);

#[derive(Id)]
pub struct OrderId(pub Nulid);

fn main() -> nulid::Result<()> {
    // Parse from &str
    let user_id = UserId::try_from("01H0JQ4VEFSBV974PRXXWEK5ZW")?;

    // Parse from String
    let user_id2 = UserId::try_from("01H0JQ4VEFSBV974PRXXWEK5ZW".to_string())?;

    // Parse using FromStr
    let user_id3: UserId = "01H0JQ4VEFSBV974PRXXWEK5ZW".parse()?;

    // Create from Nulid
    let nulid = Nulid::new()?;
    let order_id = OrderId::from(nulid);

    // Extract inner Nulid
    let back_to_nulid: Nulid = order_id.into();

    // Borrow inner Nulid
    let nulid_ref: &Nulid = order_id.as_ref();

    // Display as string
    println!("User ID: {}", user_id);

    // Direct comparison with Nulid
    assert_eq!(order_id, nulid);
    assert!(order_id <= nulid);

    Ok(())
}

Requirements

The derive macro requires:

The type must be a tuple struct
It must have exactly one field
That field must be of type Nulid

Valid examples:

#[derive(Id)]
pub struct UserId(Nulid);           // ✓ Private field

#[derive(Id)]
pub struct OrderId(pub Nulid);      // ✓ Public field

Invalid examples:

#[derive(Id)]
pub struct UserId {                 // ✗ Not a tuple struct
    nulid: Nulid,
}

#[derive(Id)]
pub struct UserId(Nulid, String);   // ✗ Multiple fields

#[derive(Id)]
pub struct UserId(String);          // ✗ Wrong type

Type Safety

Using wrapper types provides type safety by preventing accidental mixing of different ID types:

use nulid::{Nulid, Id};

#[derive(Id)]
pub struct UserId(Nulid);

#[derive(Id)]
pub struct OrderId(Nulid);

fn process_user(id: UserId) { /* ... */ }
fn process_order(id: OrderId) { /* ... */ }

let user_id = UserId::from(Nulid::new()?);
let order_id = OrderId::from(Nulid::new()?);

process_user(user_id);   // ✓ Correct type
// process_user(order_id);  // ✗ Compile error: expected UserId, found OrderId

Error Handling

All parsing methods return Result<T, nulid::Error>, allowing proper error handling:

use nulid::{Error, Id};

#[derive(Id)]
pub struct UserId(nulid::Nulid);

match UserId::try_from("invalid-string") {
    Ok(id) => println!("Parsed: {}", id),
    Err(Error::InvalidLength { expected, found }) => {
        eprintln!("Wrong length: expected {}, got {}", expected, found);
    }
    Err(Error::InvalidChar(ch, pos)) => {
        eprintln!("Invalid character '{}' at position {}", ch, pos);
    }
    Err(e) => eprintln!("Parse error: {}", e),
}

Integration with Other Traits

The derive macro works well with other derive macros:

use nulid::{Nulid, Id};

#[derive(Id)]
pub struct UserId(Nulid);

// Standard traits are automatically implemented!
// UserId now has: Debug, Copy (Clone), PartialEq, Eq, Hash, PartialOrd, Ord

// You can also add serde support if the serde feature is enabled in nulid
#[cfg(feature = "serde")]
#[derive(Id, serde::Serialize, serde::Deserialize)]
pub struct OrderId(Nulid);

Examples

See the examples directory in the nulid repository for more usage examples.

License

This project is licensed under the MIT License - see the LICENSE file for details.

nulid_derive 0.5.2