🚀 Add to your project

Add this to your Cargo.toml: toml [dependencies] impl_new = "0.2.0" Or run this command in your workspace: bash cargo add impl_new

❓ What is the new function?

The new function is a function that is used to create a new instance of a struct. It is a common pattern in Rust to use a new function to create a new instance of a struct instead of using the struct directly. This is because it is easier to add new fields to the struct without breaking the code that uses it.

👨‍💻 Usage

Is simple, just derive the impl_new::New proc macro on your struct and it will generate a new function for you.

For Named Fields

```rust

[derive(impl_new::New)]

struct Foo { name: String, age: usize, }

// The generated code will look like this: // impl Foo { // pub fn new(name: impl Into, age: Into) -> Self { // Self { name: name.into(), age: age.into() } // } // }

fn main() { let foo = Foo::new("Hello", 42usize); // Will use Into::into to convert the arguments to the fields types. asserteq!(foo.name, "Hello".tostring()); assert_eq!(foo.age, 42); } ```

For Unnamed Fields

Note: The #[impl_new(name = "name")] attribute is required for unnamed fields.

```rust

[derive(impl_new::New)]

struct Foo(#[implnew(name = "name")] String, #[implnew(name = "age")] usize);

// The generated code will look like this: // impl Foo { // pub fn new(name: impl Into, age: Into) -> Self { // Self(name.into(), age.into()) // } // }

fn main() { let foo = Foo::new("Hello", 42usize); // Will use Into::into to convert the arguments to the fields types. asserteq!(foo.0, "Hello".tostring()); assert_eq!(foo.1, 42); } ```

🛹 Attributes

#[impl_new(name = "name")]

The name option specifies the name of the argument in the new function.

Note: This attribute is required for unnamed fields.

Example

```rust

[derive(impl_new::New)]

struct User(#[implnew(name = "username")] String, #[implnew(name = "age")] i32);

// The generated code will look like this: // impl User { // pub fn new(username: impl Into, age: Into) -> Self { // Self(username.into(), age.into()) // }

fn main() { let user = User::new("Hello", 42); // Will use Into::into to convert the arguments to the fields types. asserteq!(user.0, "Hello".tostring()); assert_eq!(user.1, 42); } ```

```rust

[derive(impl_new::New)]

struct User { #[implnew(name = "username")] name: String, #[implnew(name = "user_age")] age: i32, }

// The generated code will look like this: // impl User { // pub fn new(username: impl Into, userage: Into) -> Self { // Self { name: username.into(), age: userage.into() } // } // }

fn main() { let user = User::new("Hello", 42); // Will use Into::into to convert the arguments to the fields types. asserteq!(user.name, "Hello".tostring()); assert_eq!(user.age, 42); } ```

#[impl_new(default)]

The default option will remove the field from the new function arguments and use the default value of the field type instead.

Note: This option is conflict with the name option, because the field will be removed from the new function arguments.

Example

```rust

[derive(impl_new::New, Default, Debug, PartialEq)]

struct User { name: String, #[implnew(default)] isadmin: bool, }

// The generated code will look like this: // impl User { // pub fn new(name: impl Into) -> Self { // Self { name: name.into(), is_admin: bool::default() } // } // }

[derive(impl_new::New)]

struct Foo(#[implnew(name = "somthing")] String, #[implnew(default)] User);

// The generated code will look like this: // impl Foo { // pub fn new(somthing: impl Into) -> Self { // Self(somthing.into(), User::default()) // } // }

fn main() { let user = User::new("Hello"); // Will use Into::into to convert the arguments to the fields types. let somefoo = Foo::new("Hello"); // Will use Into::into to convert the arguments to the fields types. asserteq!(user.name, "Hello".tostring()); asserteq!(user.isadmin, false); asserteq!(somefoo.0, "Hello".tostring()); asserteq!(somefoo.1, User::default()); } ```

#[impl_new(value = || <VALUE>)]

The value option will set the field value to the given value.

Note: This option is conflict with the name and default options, because the field will be removed from the new function arguments.

Note: The value must be a closure that returns the field type.

Example

```rust

[derive(impl_new::New)]

struct User { name: String, #[implnew(value = || true)] isactive: bool, }

// The generated code will look like this: (Not exactly, but you get the idea) // impl User { // pub fn new(name: impl Into) -> Self { // Self { name: name.into(), is_active: true } // } // }

[derive(impl_new::New)]

struct Foo(#[implnew(name = "name")] String, #[implnew(value = || true)] bool);

// The generated code will look like this: (Not exactly, but you get the idea) // impl Foo { // pub fn new(name: impl Into) -> Self { // Self(name.into(), true) // } // }

fn main() { let user = User::new("Bob"); // Will use Into::into to convert the arguments to the fields types. let somefoo = Foo::new("Bob"); // Will use Into::into to convert the arguments to the fields types. asserteq!(user.name, "Bob".tostring()); asserteq!(user.isactive, true); asserteq!(somefoo.0, "Bob".tostring()); asserteq!(somefoo.1, true); } ```

🤗 Contributing

Contributions are welcome! You can contribute in many ways, for example: - Improve the documentation. - Add more tests. - Add more examples. - Report a bug by opening an issue. - Suggest a new feature by opening an issue. - Fix a bug or add a new feature. (Please open an issue first if you want to add a new feature or if you want to fix a bug that doesn't have an issue yet.) - Fix a typo. - Refactor the code. - Improve the error messages.

🤝 Code of Conduct

We are committed to providing a friendly, safe and welcoming environment for all. Please read and respect the [Code of Conduct].

📝 Changelog

See [CHANGELOG.md].

🔑 License

This project is licensed under the [MIT license].