Member Variables in Rust

Full lesson:

Right now your Dog struct is just an empty shell — every Dog value you create is identical. We need a way to attach data to each object.

That's what member variables are for. A member variable is a variable that belongs to a struct — and each value created from that struct gets its own copy of every member.

Declaring member variables

struct Dog {
    pub name: String,
    pub age: i32,
}

• pub is a visibility modifier — a field declared with it is accessible from other modules. Without it, a field is private to the module where the struct is defined; code in the same file and module, like mainFunction here, can still use it.

• name: String is a regular field declaration.

Reading and writing

let mut dog = Dog { name: String::new(), age: 0 };
dog.name = String::from("Rex");        // write
dog.age = 4;
println!("{}", dog.name);  // read

Each object has its own slot for every member, so two dogs can have different names without interfering.

Your task

Update the Dog struct to have two member variables: name (a String) and age (an i32); pub is optional here. Then in mainFunction, set them on the dog value (use "Rex".to_string() for the name) so the pre-filled println! prints:

Rex is 4 years old