added exercises to \'traits\' chapter

exercises/traits/traits6.rs

@@ -0,0 +1,111 @@
+// traits6.rs
+//
+// Your task is to replace the '??' sections so the code compiles.
+// Don't change any line other than the marked one.
+// Execute `rustlings hint traits6` or use the `hint` watch subcommand for a hint.
+
+// I AM NOT DONE
+
+struct House {
+    area_sqft: u32,
+    purchase_date: String,
+}
+
+struct Vehicle {
+    name: String,
+    model: String,
+    purchase_date: String,
+}
+
+trait Details {
+    fn summary(&self) -> String;
+}
+
+impl Details for House {
+    fn summary(&self) -> String {
+        format!(
+            "The house has an area of {} sqft and was purchased on {}",
+            self.area_sqft, self.purchase_date
+        )
+    }
+}
+impl Details for Vehicle {
+    fn summary(&self) -> String {
+        format!(
+            "The {} vehicle with model {} was purchased on {}",
+            self.name, self.model, self.purchase_date
+        )
+    }
+}
+
+// TODO: Complete the code
+fn foo(flag: bool) -> ?? {
+    if flag {
+        Box::new(House {
+            area_sqft: 5000,
+            purchase_date: "21 Nov 2017".to_string(),
+        })
+    } else {
+        Box::new(Vehicle {
+            name: "BMW".to_string(),
+            model: "320d".to_string(),
+            purchase_date: "13 Aug 2022".to_string(),
+        })
+    }
+}
+
+#[cfg(test)]
+mod test {
+
+    use super::*;
+
+    fn init() -> (House, Vehicle) {
+        let house = House {
+            area_sqft: 5000,
+            purchase_date: "21 Nov 2017".to_string(),
+        };
+        let vehicle = Vehicle {
+            name: "BMW".to_string(),
+            model: "320d".to_string(),
+            purchase_date: "13 Aug 2022".to_string(),
+        };
+
+        (house, vehicle)
+    }
+
+    #[test]
+    fn check_foo_returns_house_if_true() {
+        let (house, _) = init();
+        assert_eq!(house.summary(), foo(true).summary());
+    }
+
+    #[test]
+    fn check_foo_returns_vehicle_if_false() {
+        let (_, vehicle) = init();
+        assert_eq!(vehicle.summary(), foo(false).summary());
+    }
+
+    #[test]
+    fn check_purchase_date_for_house() {
+        let (house, _) = init();
+        assert_eq!(
+            format!(
+                "The house has an area of {} sqft and was purchased on {}",
+                house.area_sqft, house.purchase_date
+            ),
+            house.summary()
+        );
+    }
+
+    #[test]
+    fn check_purchase_date_for_vehicle() {
+        let (_, vehicle) = init();
+        assert_eq!(
+            format!(
+                "The {} vehicle with model {} was purchased on {}",
+                vehicle.name, vehicle.model, vehicle.purchase_date
+            ),
+            vehicle.summary()
+        );
+    }
+}

exercises/traits/traits7.rs

@@ -0,0 +1,73 @@
+// traits7.rs
+//
+// Your task is to replace the '??' sections so the code compiles.
+// Don't change any line other than the marked one.
+// Execute `rustlings hint traits7` or use the `hint` watch subcommand for a hint.
+
+// I AM NOT DONE
+
+#[allow(unused_imports)]
+use std::fmt::{Debug, Formatter};
+
+/// Struct representing a house
+// TODO: Complete the Code
+#[derive(??, Default)]
+struct House {
+    area_sqft: u32,
+    purchase_date: String,
+}
+
+/// Struct representing a vehicle
+// TODO: Complete the Code
+#[derive(??, Default)]
+struct Vehicle {
+    name: String,
+    model: String,
+    purchase_date: String,
+}
+
+// TODO: Complete the code
+trait Details: ?? {
+    fn summary(&self) -> String;
+}
+
+impl Details for House {
+    fn summary(&self) -> String {
+        format!(
+            "The house has an area of {} sqft and was purchased on {}",
+            self.area_sqft, self.purchase_date
+        )
+    }
+}
+impl Details for Vehicle {
+    fn summary(&self) -> String {
+        format!(
+            "The {} vehicle with model {} was purchased on {}",
+            self.name, self.model, self.purchase_date
+        )
+    }
+}
+
+// TODO: Complete the code
+fn foo(flag: bool) -> ?? {
+    if flag {
+        Box::new(House {
+            area_sqft: 5000,
+            purchase_date: "21 Nov 2017".to_string(),
+        })
+    } else {
+        Box::new(Vehicle {
+            name: "BMW".to_string(),
+            model: "320d".to_string(),
+            purchase_date: "13 Aug 2022".to_string(),
+        })
+    }
+}
+
+pub fn main() {
+    let x = foo(true);
+    println!("{:?}", x);
+    // TODO: Complete the code
+    // print the summary of the struct returned from the function `foo`
+    println!("{}", ??);
+}

info.toml

@@ -737,6 +737,28 @@ To ensure a parameter implements multiple traits use the '+ syntax'. Try replaci
 See the documentation at: https://doc.rust-lang.org/book/ch10-02-traits.html#specifying-multiple-trait-bounds-with-the--syntax
 """
 
+[[exercises]]
+name = "traits6"
+path = "exercises/traits/traits6.rs"
+mode = "test"
+hint = """
+To ensure a function is able to return incompatible types can be done by using a trait bound that is common to them.
+Wrap the shared trait (implemented by the 2 struct types/objects) as a Boxed trait object. Try replacing the '??' with Box<_> 
+
+See the documentation at: https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits
+"""
+
+[[exercises]]
+name = "traits7"
+path = "exercises/traits/traits7.rs"
+mode = "compile"
+hint = """
+To make the function printable on console using `:?` symbol. Use the `Debug` trait for the `Details` trait.
+Here, if the trait implements `Debug` trait then the corresponding struct types also has to implement `Debug` trait,
+otherwise the function returning trait object will not be printable on console.
+See the documentation at: https://doc.rust-lang.org/std/fmt/trait.Debug.html
+"""
+
 # QUIZ 3
 
 [[exercises]]