TRAITS: Functions taking trait as param + returning type which implements trait

traits/src/main.rs

@@ -29,7 +29,34 @@ pub struct Tweet {
 impl Summary for Tweet {
     // Only implement summarize_author, used by summarize
     fn summarize_author(&self) -> String {
-        format!("{}", self.username)
+        format!("@{}", self.username)
+    }
+}
+
+// Shorter version but with its limitations when having multiple args
+fn notify_version_1(item: &impl Summary) {
+   println!("Breaking news! {}", item.summarize());
+}
+
+fn notify_version_2<T: Summary>(item: &T) {
+   println!("Breaking news! {}", item.summarize());
+}
+
+fn notify_version_3<T>(item: &T)
+   where T: Summary
+{
+   println!("Breaking news! {}", item.summarize());
+}
+
+// Returning a type that implements the summary trait
+fn returns_summarizable() -> impl Summary {
+    Tweet {
+        username: String::from("horse_ebooks"),
+        content: String::from(
+            "of course, as you probably already know, people",
+        ),
+        reply: false,
+        retweet: false,
     }
 }
 
@@ -47,6 +74,12 @@ fn main() {
         reply: false,
         retweet: true,
     };
+
     println!("My news article: {}", news_article.summarize());
     println!("My tweet: {}", tweet.summarize());
+
+    println!("Notification:");
+    notify_version_1(&news_article);
+    notify_version_2(&tweet);
+    notify_version_3(&returns_summarizable());
 }