quiz3 solution

exercises/quizzes/quiz3.rs

@@ -3,26 +3,27 @@
 // - 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
+// 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
+// Make the necessary code changes in the struct `ReportCard` and the impl
-// to support alphabetical report cards. Change the Grade in the second test to
+// block to support alphabetical report cards in addition to numerical ones.
-// "A+" to show that your changes allow alphabetical grades.
 
+// TODO: Adjust the struct as described above.
 struct ReportCard {
     grade: f32,
     student_name: String,
     student_age: u8,
 }
 
+// TODO: Adjust the impl block as described above.
 impl ReportCard {
     fn print(&self) -> String {
         format!(
             "{} ({}) - achieved a grade of {}",
-            &self.student_name, &self.student_age, &self.grade
+            &self.student_name, &self.student_age, &self.grade,
         )
     }
 }
@@ -44,21 +45,20 @@ mod tests {
         };
         assert_eq!(
             report_card.print(),
-            "Tom Wriggle (12) - achieved a grade of 2.1"
+            "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: 2.1,
+            grade: "A+",
             student_name: "Gary Plotter".to_string(),
             student_age: 11,
         };
         assert_eq!(
             report_card.print(),
-            "Gary Plotter (11) - achieved a grade of A+"
+            "Gary Plotter (11) - achieved a grade of A+",
         );
     }
 }

rustlings-macros/info.toml

@@ -805,10 +805,16 @@ https://doc.rust-lang.org/book/ch10-02-traits.html#specifying-multiple-trait-bou
 name = "quiz3"
 dir = "quizzes"
 hint = """
-To find the best solution to this challenge you're going to need to think back
+To find the best solution to this challenge, you need to recall your knowledge
-to your knowledge of traits, specifically 'Trait Bound Syntax'
+of traits, specifically "Trait Bound Syntax":
+https://doc.rust-lang.org/book/ch10-02-traits.html#trait-bound-syntax
 
-You may also need this: `use std::fmt::Display;`."""
+Here is how to specify a trait bound for an implementation block:
+`impl<T: Trait1 + Trait2 + …> for Foo<T> { … }`
+
+You may need this:
+`use std::fmt::Display;`
+"""
 
 # LIFETIMES
 

solutions/quizzes/quiz3.rs

@@ -1 +1,69 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+// 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 in addition to numerical ones.
+
+use std::fmt::Display;
+
+// Make the struct generic over `T`.
+struct ReportCard<T> {
+    //           ^^^
+    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> ReportCard<T> {
+    //  ^^^^^^^ require that `T` implements `Display`.
+    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+",
+        );
+    }
+}