create_getter.rs

create_getter.rs

// 1. Declarative Macro Definition
// This macro takes a field identifier ($field:ident) and generates a public
// getter method with the same name.
macro_rules! create_getter {
    ($field:ident) => {
        // The generated code:
        pub fn $field(&self) -> &str {
            // Assumes the field is a String, and returns a string slice (&str)
            &self.$field
        }
    };
}

// 2. Struct Definition
struct User {
    // The field is private by default (no 'pub'), but the generated getter is public.
    name: String,
    email: String,
}

// 3. Macro Invocation
impl User {
    // The macro call `create_getter!(name)` expands to:
    // pub fn name(&self) -> &str { &self.name }
    create_getter!(name);

    // We can also define a standard, non-macro-generated getter for 'email'
    // just to show the difference, or call the macro again:
    create_getter!(email);

    // A simple constructor for the struct
    pub fn new(name: &str, email: &str) -> Self {
        User {
            name: name.to_string(),
            email: email.to_string(),
        }
    }
}

// 4. Usage in main function
fn main() {
    let user = User::new("Alastor Moody", "[email protected]");

    // We use the getter methods generated by the macro
    let user_name: &str = user.name();
    let user_email: &str = user.email();

    println!("User Information:");
    println!("Name (via getter): {}", user_name);
    println!("Email (via getter): {}", user_email);

    // You cannot access the fields directly because they are private:
    // let private_name = user.name; // This would cause a compile error!
}

https://play.rust-lang.org/?version=stable&mode=debug&edition=2024&gist=765012841a0ef18877c70cb26a42b572