Showed how to create a lifetime in Rust

H-advanced/lifetime.rs

@@ -0,0 +1,24 @@
+
+// This will give us the Error that string2 did not live long enough
+// So that we can find where it happens
+// We declare a lifetime named 'a (it can be any letter, but 'a is standard)
+fn longest<'a>(x: &'a str, y: &'a str) -> &'a str {
+    if x.len() > y.len() {
+        x
+    } else {
+        y
+    }
+}
+
+fn main() {
+    let string1 = String::from("long_string_here");
+    let result;
+    
+    {
+        let string2 = String::from("short");
+        result = longest(string1.as_str(), string2.as_str()); 
+    } // string2 is dropped here
+    
+    // ERROR: string2 is dead, so result is invalid.
+    println!("The longest string is {}", result); 
+}