public/subjects/question_mark/README.md

question_mark

Instructions

You will have to create 3 structures:

• One, that contains one element called first_layer it should be an Option for the structure Two.
• Two, that contains one element called second_layer it should be an Option for the structure Three.
• Three, that contains one element called third_layer it should be an Option for the structure Four.
• Four, that contains one element called fourth_layer it should be an u16 that is an Option.

Beside the structure you must create a function named get_fourth_layer that is associated to the One structure. This function should return the Option value in the Four structure.

Expected Function

pub struct One {
    // expected public fields
}
pub struct Two {
    // expected public fields
}
pub struct Three {
    // expected public fields
}
pub struct Four {
    // expected public fields
}

impl One {
    pub fn get_fourth_layer(&self) -> Option<u16> {}
}

Usage

Here is a program to test your function

fn main() {
    let a = One {
        first_layer : Some(Two {
            second_layer: Some(Three {
                third_layer: Some(Four {
                    fourth_layer: Some(1000)
                })
            })
        })
    };

    // output: 1000
    println!("{:?}", match a.get_fourth_layer() {
        Some(e) => e,
        None => 0
    })
}

And its output:

student@ubuntu:~/[[ROOT]]/test$ cargo run
1000
student@ubuntu:~/[[ROOT]]/test$

Notions

• https://doc.rust-lang.org/stable/rust-by-example/error/option_unwrap/question_mark.html