Module visibility in Rust - Mini Project: Build & Apply

Understanding Module Visibility in Rust

📖 Scenario: You are building a small Rust project that organizes code into modules. You want to control which parts of your code are visible outside their modules, just like how you might decide which rooms in a house are open to guests.

🎯 Goal: Learn how to use pub to make modules and functions visible outside their module, and how to keep some parts private.

📋 What You'll Learn

Create a module named kitchen with a private function

Create a module named living_room with a public function

Use pub keyword to control visibility

Call the public function from living_room in main

Try to call the private function from kitchen in main and observe the error

💡 Why This Matters

🌍 Real World

In real Rust projects, controlling module visibility helps keep code clean and prevents accidental use of internal details.

💼 Career

Understanding module visibility is essential for writing maintainable Rust code in professional software development.

1

Create the kitchen module with a private function

Create a module called kitchen with a function named cook_food that prints "Cooking food...". Do NOT use pub before the function, so it stays private.

Rust

// Create the kitchen module with a private function cook_food
mod kitchen {
    // Your code here
}

Hint

Remember, functions are private by default in Rust modules unless you add pub.

2

Create the living_room module with a public function

Add a module called living_room with a function named watch_tv that prints "Watching TV...". Make this function public by adding pub before it.

Rust

mod kitchen {
    fn cook_food() {
        println!("Cooking food...");
    }
}

// Create the living_room module with a public function watch_tv
mod living_room {
    // Your code here
}

Hint

Use pub fn to make the function visible outside the module.

3

Call the public function from living_room in main

Write a main function that calls the public function watch_tv from the living_room module.

Rust

mod kitchen {
    fn cook_food() {
        println!("Cooking food...");
    }
}

mod living_room {
    pub fn watch_tv() {
        println!("Watching TV...");
    }
}

// Write main function to call living_room::watch_tv
fn main() {
    // Your code here
}

Hint

Use the full path living_room::watch_tv() to call the public function.

4

Try to call the private function from kitchen in main and observe the error

In the main function, add a call to kitchen::cook_food(). Run the program and observe the error message about visibility.

Rust

mod kitchen {
    fn cook_food() {
        println!("Cooking food...");
    }
}

mod living_room {
    pub fn watch_tv() {
        println!("Watching TV...");
    }
}

fn main() {
    living_room::watch_tv();
    // Try to call kitchen::cook_food() below
    // Your code here
}

Hint

This will cause a compile error because cook_food is private. This shows how Rust controls module visibility.