Rust Variables and Mutability — Understanding Ownership, Shadowing, and Constants

In this tutorial, you will learn about Rust Variables and Mutability. We cover key concepts, practical examples, and best practices to help you master this topic.

Rust variables are immutable by default with let, mutable with let mut, constants with const, and shadowing for variable reuse within scopes.

What You'll Learn

• Immutable and mutable variables
• Constants vs variables
• Shadowing
• Type annotations

Why It Matters

Rust's variable system prevents data races and bugs. Firefox uses Rust's safety guarantees. DodaZIP uses immutable variables for thread-safe config.

Real-World Use

Configuration constants, counter variables, type conversion via shadowing, safe concurrent state.

fn main() {
    let x = 5;          // Immutable
    let mut y = 10;     // Mutable
    y += 5;

    const MAX: u32 = 100;

    let z = "42";
    let z: i32 = z.parse().unwrap(); // Shadowing

    println!("x={}, y={}, max={}, z={}", x, y, MAX, z);
}