traits2 solution

exercises/15_traits/traits2.rs

@@ -1,14 +1,9 @@
-// Your task is to implement the trait `AppendBar` for a vector of strings. To
-// implement this trait, consider for a moment what it means to 'append "Bar"'
-// to a vector of strings.
-//
-// No boiler plate code this time, you can do this!
-
 trait AppendBar {
     fn append_bar(self) -> Self;
 }
 
-// TODO: Implement trait `AppendBar` for a vector of strings.
+// TODO: Implement the trait `AppendBar` for a vector of strings.
+// `appned_bar` should push the string "Bar" into the vector.
 
 fn main() {
     // You can optionally experiment here.
@@ -21,7 +16,7 @@ mod tests {
     #[test]
     fn is_vec_pop_eq_bar() {
         let mut foo = vec![String::from("Foo")].append_bar();
-        assert_eq!(foo.pop().unwrap(), String::from("Bar"));
-        assert_eq!(foo.pop().unwrap(), String::from("Foo"));
+        assert_eq!(foo.pop().unwrap(), "Bar");
+        assert_eq!(foo.pop().unwrap(), "Foo");
     }
 }

rustlings-macros/info.toml

@@ -755,21 +755,18 @@ https://doc.rust-lang.org/stable/book/ch10-01-syntax.html#in-method-definitions"
 name = "traits1"
 dir = "15_traits"
 hint = """
-A discussion about Traits in Rust can be found at:
-https://doc.rust-lang.org/book/ch10-02-traits.html
-"""
+More about traits in The Book:
+https://doc.rust-lang.org/book/ch10-02-traits.html"""
 
 [[exercises]]
 name = "traits2"
 dir = "15_traits"
 hint = """
-Notice how the trait takes ownership of `self`, and returns `Self`.
+Notice how the trait takes ownership of `self` and returns `Self`.
 
-Try mutating the incoming string vector. Have a look at the tests to see
-what the result should look like!
-
-Vectors provide suitable methods for adding an element at the end. See
-the documentation at: https://doc.rust-lang.org/std/vec/struct.Vec.html"""
+Although the signature of `append_bar` in the trait takes `self` as argument,
+the implementation can take `mut self` instead. This is possible because the
+the value is owned anyway."""
 
 [[exercises]]
 name = "traits3"

solutions/15_traits/traits2.rs

@@ -1 +1,27 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+trait AppendBar {
+    fn append_bar(self) -> Self;
+}
+
+impl AppendBar for Vec<String> {
+    fn append_bar(mut self) -> Self {
+        //        ^^^ this is important
+        self.push(String::from("Bar"));
+        self
+    }
+}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn is_vec_pop_eq_bar() {
+        let mut foo = vec![String::from("Foo")].append_bar();
+        assert_eq!(foo.pop().unwrap(), "Bar");
+        assert_eq!(foo.pop().unwrap(), "Foo");
+    }
+}