rustlings/exercises/quiz3.rs

// quiz3.rs
// This quiz tests:
// - Generics
// - Traits
// 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. Change the Grade in the second test to "A+"
// to show that your changes allow alphabetical grades.

// Execute `rustlings hint quiz3` or use the `hint` watch subcommand for a hint.

pub trait Grade {
    fn to_string(&self) -> String;
}

pub struct StrGrade(String);
pub struct NumGrade(f32);

impl Grade for StrGrade {
    fn to_string(&self) -> String {
        self.0.to_string()
    }
}
impl Grade for NumGrade {
    fn to_string(&self) -> String {
        self.0.to_string()
    }
}

pub struct ReportCard<G: Grade> {
    pub grade: G,
    pub student_name: String,
    pub student_age: u8,
}

impl<G: Grade> ReportCard<G> {
    pub fn print(&self) -> String {
        format!(
            "{} ({}) - achieved a grade of {}",
            &self.student_name,
            &self.student_age,
            &self.grade.to_string()
        )
    }
}

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

    #[test]
    fn generate_numeric_report_card() {
        let report_card = ReportCard {
            grade: NumGrade(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() {
        // TODO: Make sure to change the grade here after you finish the exercise.
        let report_card = ReportCard {
            grade: StrGrade(String::from("A+")),
            student_name: "Gary Plotter".to_string(),
            student_age: 11,
        };
        assert_eq!(
            report_card.print(),
            "Gary Plotter (11) - achieved a grade of A+"
        );
    }
}