Getters and Setters in Rust in Rust

struct Dog {
    age: i32,
}

impl Dog {
    fn new(age: i32) -> Dog {
        Dog { age: age }
    }

    fn get_age(&self) -> i32 {
        self.age
    }

    fn set_age(&mut self, value: i32) {
        if value >= 0 {
            self.age = value;
        }
    }
}

Full lesson:

In the Access Modifiers lesson, get_name let other code read a private field. Often other code must change a field too. A setter allows that, and it checks each new value first.

The getter

The getter only reads, so it takes &self. Its body is self.age, without a semicolon.

The setter

The setter changes the struct, so it takes &mut self. That's why rex is declared with let mut. Other code calls rex.set_age(4).

The rule

A dog's age can't be negative. So set_age changes self.age only when value is 0 or more. After rex.set_age(-5), the age stays as it was.

Why not a pub field?

With pub age, code in other modules could set it to -5. Nothing would check it. The setter keeps the rule inside the impl block.

Your task

The Dog struct keeps its age in the private field age. Add a getter get_age that returns it. Add a setter set_age that ignores negative values.

The code in main_function creates rex, then reads and sets its age.

Expected output:

Rex is 3
Rex is still 3
Rex is 4