From 5626a54d626cfe520ba879c42fc9dd0331c76eb9 Mon Sep 17 00:00:00 2001
From: Jordan Gong <jordan.gong@protonmail.com>
Date: Wed, 2 Sep 2020 21:00:12 +0800
Subject: Share behavior with traits

---
 traits/src/lib.rs  | 78 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 traits/src/main.rs | 26 ++++++++++++++++++
 2 files changed, 104 insertions(+)
 create mode 100644 traits/src/lib.rs
 create mode 100644 traits/src/main.rs

(limited to 'traits/src')

diff --git a/traits/src/lib.rs b/traits/src/lib.rs
new file mode 100644
index 0000000..a0255ea
--- /dev/null
+++ b/traits/src/lib.rs
@@ -0,0 +1,78 @@
+pub trait Summary {
+    fn summarize(&self) -> String {
+        // default implementarion
+        format!("(Read more from {}...)", self.summarize_author())
+    }
+
+    fn summarize_author(&self) -> String {
+        String::from("Anonymous")
+    }
+}
+
+pub struct NewsArticle {
+    pub headline: String,
+    pub location: String,
+    pub author: String,
+    pub content: String,
+}
+
+impl Summary for NewsArticle {
+    fn summarize(&self) -> String {
+        format!("{}, by {} ({})", self.headline, self.author, self.location)
+    }
+
+    // fn summarize_author(&self) -> String {
+    //     format!("{}", self.author)
+    // }
+}
+
+pub struct Tweet {
+    pub username: String,
+    pub content: String,
+    pub reply: bool,
+    pub retweet: bool,
+}
+
+impl Summary for Tweet {
+    // fn summarize(&self) -> String {
+    //     format!("{}: {}", self.username, self.content)
+    // }
+
+    fn summarize_author(&self) -> String {
+        format!("@{}", self.username)
+    }
+}
+
+// Traits as parameter
+// pub fn notify(item: &impl Summary) {
+//     println!("Breaking news! {}", item.summarize());
+// }
+
+// Trait bound syntax
+pub fn notify<T: Summary>(item: &T) {
+    println!("Breaking news! {}", item.summarize());
+}
+
+// statements below are equivalent
+// pub fn nofity(item1: &impl Summary, item2: Summary) {}
+// pub fn nofity<T: Summary>(item1: &T, item2: &T) {}
+
+// use std::fmt::Display;
+// multiple bound
+// pub fn notify(item: &(impl Summary + Display)) {}
+// or
+// pub fn notify<T: Summary + Display>(item: &T) {}
+// where clause
+// pub fn notify<T>(item: &T)
+//     where T: Summary + Display
+// {}
+
+// return impl Trait
+fn return_summarizble() -> impl Summary {
+    Tweet {
+        username: String::from("horse_ebooks"),
+        content: String::from("of course, as you probably already know, people"),
+        reply: false,
+        retweet: false,
+    }
+}
diff --git a/traits/src/main.rs b/traits/src/main.rs
new file mode 100644
index 0000000..02e408b
--- /dev/null
+++ b/traits/src/main.rs
@@ -0,0 +1,26 @@
+use traits::{self, NewsArticle, Summary, Tweet, notify};
+
+fn main() {
+    let tweet = Tweet {
+        username: String::from("horse_ebooks"),
+        content: String::from("of course, as you probably already know, people"),
+        reply: false,
+        retweet: false,
+    };
+
+    println!("1 new tweet: {}", tweet.summarize());
+
+    let article = NewsArticle {
+        headline: String::from("Penguins win the Stanley Cup Championship!"),
+        location: String::from("Pittsburgh, PA, USA"),
+        author: String::from("Iceburgh"),
+        content: String::from(
+            "The Pittsburgh Penguins once again are the best \
+             hockey team in the NHL.",
+        ),
+    };
+
+    println!("New article available! {}", article.summarize());
+
+    notify(&article);
+}
-- 
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