rustlings: complete 16

7 files changed, 75 insertions, 13 deletions

diff --git a/rustlings/.rustlings-state.txt b/rustlings/.rustlings-state.txt
index 888d577..e366df4 100644
--- a/rustlings/.rustlings-state.txt
+++ b/rustlings/.rustlings-state.txt
@@ -1,6 +1,6 @@
 DON'T EDIT THIS FILE!
 
-lifetimes1
+tests1
 
 intro1
 intro2
@@ -65,4 +65,7 @@ traits2
 traits3
 traits4
 traits5
-quiz3
\ No newline at end of file
+quiz3
+lifetimes1
+lifetimes2
+lifetimes3
\ No newline at end of file
diff --git a/rustlings/exercises/16_lifetimes/lifetimes1.rs b/rustlings/exercises/16_lifetimes/lifetimes1.rs
index 19e2d39..683bd75 100644
--- a/rustlings/exercises/16_lifetimes/lifetimes1.rs
+++ b/rustlings/exercises/16_lifetimes/lifetimes1.rs
@@ -4,7 +4,7 @@
 // not own their own data. What if their owner goes out of scope?
 
 // TODO: Fix the compiler error by updating the function signature.
-fn longest(x: &str, y: &str) -> &str {
+fn longest<'a>(x: &'a str, y: &'a str) -> &'a str {
     if x.len() > y.len() {
         x
     } else {
diff --git a/rustlings/exercises/16_lifetimes/lifetimes2.rs b/rustlings/exercises/16_lifetimes/lifetimes2.rs
index de5a5df..ebbc99c 100644
--- a/rustlings/exercises/16_lifetimes/lifetimes2.rs
+++ b/rustlings/exercises/16_lifetimes/lifetimes2.rs
@@ -11,9 +11,9 @@ fn main() {
     // TODO: Fix the compiler error by moving one line.
 
     let string1 = String::from("long string is long");
+    let string2 = String::from("xyz");
     let result;
     {
-        let string2 = String::from("xyz");
         result = longest(&string1, &string2);
     }
     println!("The longest string is '{result}'");
diff --git a/rustlings/exercises/16_lifetimes/lifetimes3.rs b/rustlings/exercises/16_lifetimes/lifetimes3.rs
index 1cc2759..91e3922 100644
--- a/rustlings/exercises/16_lifetimes/lifetimes3.rs
+++ b/rustlings/exercises/16_lifetimes/lifetimes3.rs
@@ -1,9 +1,9 @@
 // Lifetimes are also needed when structs hold references.
 
 // TODO: Fix the compiler errors about the struct.
-struct Book {
-    author: &str,
-    title: &str,
+struct Book<'a> {
+    author: &'a str,
+    title: &'a str,
 }
 
 fn main() {
diff --git a/rustlings/solutions/16_lifetimes/lifetimes1.rs b/rustlings/solutions/16_lifetimes/lifetimes1.rs
index dcf2377..4f56834 100644
--- a/rustlings/solutions/16_lifetimes/lifetimes1.rs
+++ b/rustlings/solutions/16_lifetimes/lifetimes1.rs
@@ -1,4 +1,24 @@
+// The Rust compiler needs to know how to check whether supplied references are
+// valid, so that it can let the programmer know if a reference is at risk of
+// going out of scope before it is used. Remember, references are borrows and do
+// not own their own data. What if their owner goes out of scope?
+
+fn longest<'a>(x: &'a str, y: &'a str) -> &'a str {
+    //    ^^^^     ^^          ^^          ^^
+    if x.len() > y.len() { x } else { y }
+}
+
 fn main() {
-    // DON'T EDIT THIS SOLUTION FILE!
-    // It will be automatically filled after you finish the exercise.
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_longest() {
+        assert_eq!(longest("abcd", "123"), "abcd");
+        assert_eq!(longest("abc", "1234"), "1234");
+    }
 }
diff --git a/rustlings/solutions/16_lifetimes/lifetimes2.rs b/rustlings/solutions/16_lifetimes/lifetimes2.rs
index dcf2377..3ca4909 100644
--- a/rustlings/solutions/16_lifetimes/lifetimes2.rs
+++ b/rustlings/solutions/16_lifetimes/lifetimes2.rs
@@ -1,4 +1,29 @@
+fn longest<'a>(x: &'a str, y: &'a str) -> &'a str {
+    if x.len() > y.len() { x } else { y }
+}
+
 fn main() {
-    // DON'T EDIT THIS SOLUTION FILE!
-    // It will be automatically filled after you finish the exercise.
+    let string1 = String::from("long string is long");
+    // Solution1: You can move `strings2` out of the inner block so that it is
+    // not dropped before the print statement.
+    let string2 = String::from("xyz");
+    let result;
+    {
+        result = longest(&string1, &string2);
+    }
+    println!("The longest string is '{result}'");
+    // `string2` dropped at the end of the function.
+
+    // =========================================================================
+
+    let string1 = String::from("long string is long");
+    let result;
+    {
+        let string2 = String::from("xyz");
+        result = longest(&string1, &string2);
+        // Solution2: You can move the print statement into the inner block so
+        // that it is executed before `string2` is dropped.
+        println!("The longest string is '{result}'");
+        // `string2` dropped here (end of the inner scope).
+    }
 }
diff --git a/rustlings/solutions/16_lifetimes/lifetimes3.rs b/rustlings/solutions/16_lifetimes/lifetimes3.rs
index dcf2377..16a5a68 100644
--- a/rustlings/solutions/16_lifetimes/lifetimes3.rs
+++ b/rustlings/solutions/16_lifetimes/lifetimes3.rs
@@ -1,4 +1,18 @@
+// Lifetimes are also needed when structs hold references.
+
+struct Book<'a> {
+    //     ^^^^ added a lifetime annotation
+    author: &'a str,
+    //       ^^
+    title: &'a str,
+    //      ^^
+}
+
 fn main() {
-    // DON'T EDIT THIS SOLUTION FILE!
-    // It will be automatically filled after you finish the exercise.
+    let book = Book {
+        author: "George Orwell",
+        title: "1984",
+    };
+
+    println!("{} by {}", book.title, book.author);
 }