generics and lifetimes

generics/media-aggregator/Cargo.toml

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+[package]
+name = "media-aggregator"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]

generics/media-aggregator/src/lib.rs

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+use ::std::fmt::Display;
+use std::fmt::Debug;
+pub trait Summary {
+    fn summarize_author(&self) -> String;
+
+    fn summarize(&self) -> String {
+        // "(Read more...)".to_string()
+        let x = "a".to_string();
+        x
+    }
+}
+
+#[derive(Debug)]
+pub struct NewsArticle {
+    pub headline: String,
+    pub location: String,
+    pub author: String,
+    pub content: String,
+}
+
+#[derive(Debug)]
+pub struct SocialPost {
+    pub username: String,
+    pub content: String,
+    pub reply: bool,
+    pub repost: bool,
+}
+
+impl Summary for NewsArticle {
+    // fn summarize(&self) -> String {
+    // format!("{}, by {} ({})", self.headline, self.author, self.location)
+    // }
+    fn summarize_author(&self) -> String {
+        "trad media".to_string() // format!("@{}", self.author)
+    }
+}
+
+// impl Summary for SocialPost {
+//     fn summarize(&self) -> String {
+//         format!("{} by {}", self.content, self.summarize_author())
+//     }
+//
+//     fn summarize_author(&self) -> String {
+//         format!("@{}", self.username)
+//     }
+// }
+
+// pub fn notify(item: &impl Summary) {
+// println!("{}", item.summarize());
+// }
+
+pub fn notify<T, U>(item: &T, x: U)
+where
+    T: Summary,
+    U: Copy + Debug + Display + Clone,
+{
+    println!("{}", item.summarize());
+    let y = x;
+    println!("doubled: {:?}", y);
+}

generics/media-aggregator/src/main.rs

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+use media_aggregator::{NewsArticle, SocialPost};
+use media_aggregator::{Summary, notify};
+
+fn main() {
+    let article = NewsArticle {
+        headline: "Chancellor on brink of second bailout for banks".to_string(),
+        location: "London".to_string(),
+        author: "The Times".to_string(),
+        content: "Please subscribe to Premium to read the whole story.".to_string(),
+    };
+
+    let tweet = SocialPost {
+        content: "running bitcoin".to_string(),
+        username: "halfin".to_string(),
+        reply: false,
+        repost: false,
+    };
+
+    println!("\n --- DEBUG: values ---");
+    println!("{:?}", article);
+    // println!("{:?}", tweet);
+
+    println!("\n --- DEBUG: article summary ---");
+    println!("{:?}", article.summarize());
+
+    println!("\n --- DEBUG: article notify---");
+    notify(&article, 5);
+}