rust mutability

main.rs

#[derive(Debug)]
struct Parent {
    child: Child,
}
#[derive(Debug)]
struct Child {
    name: String,
}

fn main() {
    println!("Hello, world!");

    non_mutable();
    mutable_parent();
}

fn non_mutable() {
    let child = Child {
        name: String::from("Alice"),
    };
    let parent = Parent {
        child: child,
    };
    // println!("{:#?}", parent);
    // parent.child_one.name = String::from("Carol")
    // cannot mutably borrow field of immutable binding
}

fn mutable_child() {
    let mut mut_child = Child {
        name: String::from("Alice"),
    };
    let parent = Parent {
        child: mut_child,
    };
    // println!("{:#?}", parent);
    // parent.child.name = String::from("Carol")
    // cannot mutably borrow field of immutable binding
}

fn mutable_parent() {
    let child = Child {
        name: String::from("Alice"),
    };
    let mut parent = Parent {
        child: child,
    };
    println!("{:#?}", parent);
    // return
    // Parent {
    //     child: Child {
    //         name: "Alice"
    //     }
    // }

    parent.child.name = String::from("Carol");
    println!("{:#?}", parent);
    // return
    // Parent {
    //     child: Child {
    //         name: "Carol"
    //     }
    // }
}