public/subjects/borrow_box/README.md

borrow box

Instructions

Game time.

You will implement some CRUD functionality for a game session. You will need to implement the GameSession structure with the following associated functions:

• new: which initializes a game session state with player names and some other information. This function returns the structure wrapped in a Box.

• read_winner: which returns a tuple with the name and score of the player who is currently winning. In the case that no player is winning, it should return the same tuple with the string "Same score! tied" and the tied score.

• update_score: which receives the name of a player, and increments their score. This function should do nothing if the the game session is already finished.

• delete: which takes ownership of the boxed game session and returns a string: "game deleted: id -> 0".

If nb_games is 5, then it is "best out of 5", and no more than 5 games can be played. If some player has a score of 3, then the game session is also finished. This is because there is an insufficient number of remaining games for the trailing player to catch up.

Expected Functions

#[derive(Debug, Clone, Eq, PartialEq)]
pub struct GameSession {
    pub id: u32,
    pub p1: (String, u16),
    pub p2: (String, u16),
    pub nb_games: u16
}

impl GameSession {
    pub fn new(id: u32, p1_name: String, p2_name: String, nb_games: u16) -> Box<GameSession> {

    }
    pub fn read_winner(&self) -> (String, u16) {

    }
    pub fn update_score(&mut self, user_name: String) {

    }
    pub fn delete(self) -> String {

    }
}

Usage

Here is a program to test your functions,

use borrow_box::*;

fn main() {
    let mut game = GameSession::new(0, String::from("Joao"), String::from("Susana"), 5);
    println!("{:?}", game.read_winner());
    // output : ("Same score! tied", 0)

    game.update_score(String::from("Joao"));
    game.update_score(String::from("Joao"));
    game.update_score(String::from("Susana"));
    game.update_score(String::from("Susana"));
    println!("{:?}", game.read_winner());
    // output : ("Same score! tied", 2)

    game.update_score(String::from("Joao"));
    // this one will not count because it already 5 games played, the nb_games
    game.update_score(String::from("Susana"));

    println!("{:?}", game.read_winner());
    // output : ("Joao", 3)

    println!("{:?}", game.delete());
    // output : "game deleted: id -> 0"

    // game.read_winner();
    // this will give error
    // because the game was dropped, no longer exists on the heap
}

And its output:

$ cargo run
("Same score! tied", 0)
("Same score! tied", 2)
("Joao", 3)
"game deleted: id -> 0"
$

Notions

• Box Pointers