rustlings/solutions/quizzes/quiz3.rs

// An imaginary magical school has a new report card generation system written
// in Rust! Currently, the system only supports creating report cards where the
// student's grade is represented numerically (e.g. 1.0 -> 5.5). However, the
// school also issues alphabetical grades (A+ -> F-) and needs to be able to
// print both types of report card!
//
// Make the necessary code changes in the struct `ReportCard` and the impl
// block to support alphabetical report cards in addition to numerical ones.

use std::fmt::Display;

// Grade Trait
trait Grade {}
//^^^^^^^^^^^^

// Implements the trait for `f32` (numeric, e.g. 1.0 -> 5.5)
impl Grade for f32 {}
//^^^^^^^^^^^^^^^^^^^

// Implements the trait for `str` (alphabetic, A+ -> F-)
impl Grade for &str {}
//^^^^^^^^^^^^^^^^^^^^

// Make the struct generic over `T: Grade`.
struct ReportCard<T: Grade> {
    //           ^^^^^^^^^^
    grade: T,
    //     ^
    student_name: String,
    student_age: u8,
}

// To be able to print the grade, it has to implement the `Display` trait.
impl<T: Display + Grade> ReportCard<T> {
    //  ^^^^^^^^^^^^^^^ require that `T` implements `Display` and `Grade`.
    fn print(&self) -> String {
        format!(
            "{} ({}) - achieved a grade of {}",
            &self.student_name, &self.student_age, &self.grade,
        )
    }
}

fn main() {
    // You can optionally experiment here.
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn generate_numeric_report_card() {
        let report_card = ReportCard {
            grade: 2.1,
            student_name: "Tom Wriggle".to_string(),
            student_age: 12,
        };
        assert_eq!(
            report_card.print(),
            "Tom Wriggle (12) - achieved a grade of 2.1",
        );
    }

    #[test]
    fn generate_alphabetic_report_card() {
        let report_card = ReportCard {
            grade: "A+",
            student_name: "Gary Plotter".to_string(),
            student_age: 11,
        };
        assert_eq!(
            report_card.print(),
            "Gary Plotter (11) - achieved a grade of A+",
        );
    }
}