Add traits example

traits/src/main.rs

@@ -0,0 +1,57 @@
+pub trait Summary {
+    fn summarize_author(&self) -> String;
+
+    fn summarize(&self) -> String {
+        format!("(Read more from {}...)", self.summarize_author())
+    }
+}
+
+pub struct NewsArticle {
+    pub headline: String,
+    pub location: String,
+    pub author: String,
+    pub content: String,
+}
+
+impl Summary for NewsArticle {
+    // We have to provide an implementation for all methods without default implementation!
+    fn summarize_author(&self) -> String {
+        format!("{}", self.author)
+    }
+
+    fn summarize(&self) -> String {
+        format!("{}, by {} ({})", self.headline, self.author, self.location)
+    }
+}
+
+pub struct Tweet {
+    pub username: String,
+    pub content: String,
+    pub reply: bool,
+    pub retweet: bool,
+}
+
+impl Summary for Tweet {
+    // Only implement summarize_author, used by summarize
+    fn summarize_author(&self) -> String {
+        format!("{}", self.username)
+    }
+}
+
+fn main() {
+    let news_article = NewsArticle {
+        headline: "My awesome headline".to_string(),
+        location: "here".to_string(),
+        author: "me".to_string(),
+        content: "Something".to_string(),
+    };
+
+    let tweet = Tweet {
+        username: "My cool username".to_string(),
+        content: "Something in a tweet".to_string(),
+        reply: false,
+        retweet: true,
+    };
+    println!("My news article: {}", news_article.summarize());
+    println!("My tweet: {}", tweet.summarize());
+}