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Module Multiple files

Rust allows modules to be split across multiple files. This helps organize larger projects and keeps files manageable.

cargo new moddemo2

create files as given below

departments.rs

pub mod dept {
    fn get_number(num: i32) -> String {
        match num {
            1 => return "123-456-7890".to_string(),
            2 => return "987-654-3210".to_string(),
            _ => return "000-000-0000".to_string(),
        }
    }

    pub mod sales {
        pub fn meet_customer(num: i32) {
            println!("Sales : meet customer {num}");
            let phone_number = super::get_number(num);
            println!("Sales calling {}", phone_number);
        }
    }

    pub mod service {
        pub fn meet_customer(num: i32) {
            println!("Service : meet customer {num}");
            let phone_number = super::get_number(num);
            let ticket_number = self::get_service_ticket_number(num);
            println!("Calling {phone_number} with ticket number {ticket_number}");
        }

        fn get_service_ticket_number(num: i32) -> i32 {
            match num {
                1 => return 2452423,
                2 => return 2341332,
                _ => return 6868765,
            }
        }
    }

    #[cfg(test)] // Only compiles when running tests
    mod tests {
        use crate::get_standard_greetings;

        #[test]
        fn test_customerphone() {
            assert_eq!("000-000-0000", super::get_number(4));
        }

        #[test]
        fn test_standard_greeting() {
            assert_eq!("Welcome to our store.", get_standard_greetings());
        }
    }
}

main.rs

// Refer the external file
mod departments;

// Import the module
use departments::dept;

fn main() {
    println!("{:?}", get_standard_greetings());
    dept::sales::meet_customer(1);
    dept::service::meet_customer(3);
}

fn get_standard_greetings() -> String {
    return "Welcome to our store.".to_string();
}

• mod departments; tells Rust to load the module from departments.rs
• use departments::dept; imports the module so we can reference it easily
• Functions inside the module can be accessed using the module path

main.rs
|
|-- mod departments
|
|-- departments.rs
|
|-- pub mod dept

Run the program

cargo run

Test the program

cargo test

#module #externalfileVer 2.0.19