Struct visibility - Rust By Example
Description: A description

# Struct visibility

Structs have an extra level of visibility with their fields. The visibility defaults to private, and can be overridden with the `pub` modifier. This visibility only matters when a struct is accessed from outside the module where it is defined, and has the goal of hiding information (encapsulation).

    mod my {
        // A public struct with a public field of generic type `T`
        pub struct OpenBox<T> {
            pub contents: T,
        }

        // A public struct with a private field of generic type `T`
        #[allow(dead_code)]
        pub struct ClosedBox<T> {
            contents: T,
        }

        impl<T> ClosedBox<T> {
            // A public constructor method
            pub fn new(contents: T) -> ClosedBox<T> {
                ClosedBox {
                    contents: contents,
                }
            }
        }
    }

    fn main() {
        // Public structs with public fields can be constructed as usual
        let open_box = my::OpenBox { contents: "public information" };

        // and their fields can be normally accessed.
        println!("The open box contains: {}", open_box.contents);

        // Public structs with private fields cannot be constructed using field names.
        // Error! `ClosedBox` has private fields
        //let closed_box = my::ClosedBox { contents: "classified information" };
        // TODO ^ Try uncommenting this line

        // However, structs with private fields can be created using
        // public constructors
        let _closed_box = my::ClosedBox::new("classified information");

        // and the private fields of a public struct cannot be accessed.
        // Error! The `contents` field is private
        //println!("The closed box contains: {}", _closed_box.contents);
        // TODO ^ Try uncommenting this line
    }

### See also:

generics and methods