strings 3 solution

exercises/09_strings/strings3.rs

@@ -1,16 +1,13 @@
-fn trim_me(input: &str) -> String {
-    // TODO: Remove whitespace from both ends of a string!
-    ???
+fn trim_me(input: &str) -> &str {
+    // TODO: Remove whitespace from both ends of a string.
 }
 
 fn compose_me(input: &str) -> String {
-    // TODO: Add " world!" to the string! There are multiple ways to do this!
-    ???
+    // TODO: Add " world!" to the string! There are multiple ways to do this.
 }
 
 fn replace_me(input: &str) -> String {
-    // TODO: Replace "cars" in the string with "balloons"!
-    ???
+    // TODO: Replace "cars" in the string with "balloons".
 }
 
 fn main() {
@@ -36,7 +33,13 @@ mod tests {
 
     #[test]
     fn replace_a_string() {
-        assert_eq!(replace_me("I think cars are cool"), "I think balloons are cool");
-        assert_eq!(replace_me("I love to look at cars"), "I love to look at balloons");
+        assert_eq!(
+            replace_me("I think cars are cool"),
+            "I think balloons are cool",
+        );
+        assert_eq!(
+            replace_me("I love to look at cars"),
+            "I love to look at balloons",
+        );
     }
 }

rustlings-macros/info.toml

@@ -499,7 +499,8 @@ https://doc.rust-lang.org/stable/book/ch15-02-deref.html#implicit-deref-coercion
 name = "strings3"
 dir = "09_strings"
 hint = """
-There's tons of useful standard library functions for strings. Let's try and use some of them:
+There are many useful standard library functions for strings. Let's try and use
+some of them:
 https://doc.rust-lang.org/std/string/struct.String.html#method.trim
 
 For the `compose_me` method: You can either use the `format!` macro, or convert

solutions/09_strings/strings3.rs

@@ -1 +1,48 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+fn trim_me(input: &str) -> &str {
+    input.trim()
+}
+
+fn compose_me(input: &str) -> String {
+    // The macro `format!` has the same syntax as `println!`, but it returns a
+    // string instead of printing it to the terminal.
+    // Equivalent to `input.to_string() + " world!"`
+    format!("{input} world!")
+}
+
+fn replace_me(input: &str) -> String {
+    input.replace("cars", "balloons")
+}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn trim_a_string() {
+        assert_eq!(trim_me("Hello!     "), "Hello!");
+        assert_eq!(trim_me("  What's up!"), "What's up!");
+        assert_eq!(trim_me("   Hola!  "), "Hola!");
+    }
+
+    #[test]
+    fn compose_a_string() {
+        assert_eq!(compose_me("Hello"), "Hello world!");
+        assert_eq!(compose_me("Goodbye"), "Goodbye world!");
+    }
+
+    #[test]
+    fn replace_a_string() {
+        assert_eq!(
+            replace_me("I think cars are cool"),
+            "I think balloons are cool",
+        );
+        assert_eq!(
+            replace_me("I love to look at cars"),
+            "I love to look at balloons",
+        );
+    }
+}