Crate impl_new_derive

impl_new_derive

ImplNew is a Rust procedural macro that automatically generates a constructor (new method) for structs with named fields. It initializes public fields from provided arguments, and private fields are automatically initialized using Default::default().

Features

• Automatic constructor generation: Generates a new method for structs.
• Public fields: Public fields are passed as parameters to the new method.
• Private fields: Private fields are initialized with Default::default().
• Generics support: The macro works for both generic and non-generic structs.

Usage

Add the following dependency to your Cargo.toml file to use the macro:

[dependencies]
impl_new_derive = "0.1.0"

Then, annotate your struct with #[derive(ImplNew)] to generate the new method.

Example for a Non-Generic Struct

use impl_new_derive::ImplNew;

#[derive(ImplNew, Default)]
struct MyStruct {
    pub name: String,
    pub age: u32,
    secret: String, // This field is private
}

fn main() {
    let my_struct = MyStruct::new("John".to_string(), 30);
    println!("Name: {}, Age: {}", my_struct.name, my_struct.age);
}

In this example:

• name and age are public fields and are passed as arguments to the new function.
• secret is a private field and is automatically initialized to its default value.

Example for a Generic Struct

use impl_new_derive::ImplNew;

#[derive(ImplNew, Default)]
struct MyStruct<T> {
    pub value: T,
    count: usize, // This field is private
}

fn main() {
    let my_struct = MyStruct::new(42);
    println!("Value: {}", my_struct.value);
}

How It Works

When the ImplNew macro is applied to a struct, the macro performs the following actions:

• Iterates over the struct’s fields.
• Public fields are added as parameters to the generated new function.
• Non-public fields are initialized with Default::default().
• If the struct contains generics, the macro correctly handles them in the impl block.

Limitations

• The ImplNew macro only works for structs with named fields.
• Private fields must implement Default, or the macro will fail to compile.

License

Licensed under the MIT License.

Derive Macros

ImplNew