Derive Macro New 

#[derive(New)]
{
    // Attributes available to this derive:
    #[new]
}

A procedural macro that generates a constructor function for structs.

This macro automatically generates a new function that takes all non-skipped fields as parameters and returns a new instance of the struct. Fields marked with #[new(skip)] will be initialized with their default values.

Supported Attributes

• #[new(skip)] - Excludes the field from constructor parameters and uses default initialization
• #[new(pub)] - Generates a public constructor
• #[new(pub(crate))] - Generates a crate-visible constructor
• #[new(pub(super))] - Generates a constructor visible to parent module
• #[new(private)] - Generates a private constructor

Default Behavior

• The generated constructor is pub by default
• All fields are included in the constructor unless marked with #[new(skip)]
• Skipped fields are initialized using Default::default()

Examples

Basic Usage

use lombok_macros::*;

#[derive(New)]
struct Person {
    name: String,
    age: u32,
}

let person = Person::new("Alice".to_string(), 30);
assert_eq!(person.name, "Alice");
assert_eq!(person.age, 30);

With Skip Attribute

use lombok_macros::*;

#[derive(New)]
struct User {
    username: String,
    email: String,
    #[new(skip)]
    created_at: String,
}

let user = User::new("alice".to_string(), "alice@ltpp.vip".to_string());
assert_eq!(user.username, "alice");
assert_eq!(user.email, "alice@ltpp.vip");
assert_eq!(user.created_at, "");

With Custom Visibility

use lombok_macros::*;

#[derive(New)]
#[new(pub(crate))]
struct InternalStruct {
    value: i32,
}

let internal = InternalStruct::new(42);
assert_eq!(internal.value, 42);

Tuple Structs

use lombok_macros::*;

#[derive(New)]
struct Point(
    f64,
    f64,
);

let origin = Point::new(0.0, 0.0);
assert_eq!(origin.0, 0.0);
assert_eq!(origin.1, 0.0);

Generic Types

use lombok_macros::*;

#[derive(New)]
struct Container<T: Default + Clone> {
    data: T,
    #[new(skip)]
    count: usize,
}

let container = Container::new("data".to_string());
assert_eq!(container.data, "data");
assert_eq!(container.count, 0);

Arguments

• input - The input token stream representing the struct for which to generate the constructor.

Returns

• TokenStream - The generated constructor implementation.