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p16.fearless_conscurrency/shared_trait/.gitignore

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+/target

p16.fearless_conscurrency/shared_trait/Cargo.toml

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+[package]
+name = "shared_trait"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

p16.fearless_conscurrency/shared_trait/src/lib.rs

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+//定义一个Draw trait，所有实现了Draw trait的类型都要具有draw方法。
+pub trait Draw {
+    fn draw(&self);
+}
+
+pub struct Screen {
+    pub components: Vec<Box<dyn Draw>>,
+}
+
+impl Screen {
+    pub fn new() -> Screen {
+        Screen { components: vec![] }
+    }
+    pub fn add(&mut self, comp: Box<dyn Draw>) {
+        self.components.push(comp)
+    }
+    pub fn run(&self) {
+        if self.components.len() == 0 {
+            println!("has no components!");
+            return;
+        }
+        for obj in self.components.iter() {
+            obj.draw();
+        }
+    }
+}
+
+pub struct Button {
+    width: u32,
+    height: u32,
+    text: String,
+}
+
+impl Button {
+    pub fn new(width: u32, height: u32, text: &str) -> Button {
+        Button {
+            width,
+            height,
+            text: String::from(text),
+        }
+    }
+}
+
+impl Draw for Button {
+    fn draw(&self) {
+        println!(
+            "This is a Button, draw by {}x{} : {}",
+            self.width, self.height, self.text
+        );
+    }
+}

p16.fearless_conscurrency/shared_trait/src/main.rs

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+use shared_trait::*;
+
+struct SelectBox<'a> {
+    width: i32,
+    height: u32,
+    option: Vec<&'a str>,
+}
+
+impl<'a> Draw for SelectBox<'a> {
+    fn draw(&self) {
+        println!(
+            "This is a Button, draw by {}x{} : {:?}",
+            self.width, self.height, self.option
+        );
+    }
+}
+
+fn main() {
+    println!("Hello, world!");
+    let mut screen = Screen::new();
+
+    let button = Button::new(30, 40, "Button text");
+    screen.add(Box::new(button));
+    screen.add(Box::new(SelectBox {
+        width: 100,
+        height: 300,
+        option: vec!["option1", "option2", "option3"],
+    }));
+
+    // screen.add(Box::new(String::from("asdad"))); //the trait bound `String: shared_trait::Draw` is not satisfied
+    screen.run();
+}