Rust learning: lessons, notes, and exercise crates

learn-struct/.gitignore

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+/target

learn-struct/Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "learn-struct"
+version = "0.1.0"

learn-struct/Cargo.toml

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+[package]
+name = "learn-struct"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]

learn-struct/src/main.rs

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+struct User {
+    active: bool,
+    username: String,
+    email: String,
+    sign_in_count: usize,
+}
+
+#[derive(Debug)]
+struct Rectangle {
+    width: u32,
+    height: u32,
+}
+
+impl Rectangle {
+    fn area(&self) -> u32 {
+        self.width * self.height
+    }
+
+    fn width(&self) -> bool {
+        self.width > 0
+    }
+
+    fn square(size: u32) -> Self {
+        Self {
+            width: size,
+            height: size,
+        }
+    }
+}
+
+fn main() {
+    println!("Hello, world!");
+    let mut user1 = User {
+        active: true,
+        username: String::from("username123"),
+        email: String::from("user@ecample.com"),
+        sign_in_count: 2,
+    };
+
+    user1.username = String::from("kiki");
+
+    let user2 = build_user("email@asl.com", "kiki");
+
+    let _user3 = User {
+        active: false,
+        ..user2
+    };
+
+    // println!("{}", user2.username); //Error because the username is a String on heap and its already moved to the user3
+
+    let rect1 = Rectangle {
+        width: 30,
+        height: 20,
+    };
+    println!(
+        "this is the area of the rect {} square pixels",
+        rect1.area()
+    );
+
+    println!("rect is {rect1:?}");
+
+    if rect1.width() {
+        println!("The rectange have width")
+    }
+
+    let rect2 = Rectangle::square(42);
+
+    println!(
+        "this is the area of the rect2 {} square pixels",
+        rect2.area()
+    );
+}
+
+fn build_user(email: &str, username: &str) -> User {
+    User {
+        active: true,
+        username: String::from(username),
+        email: String::from(email),
+        sign_in_count: 2,
+    }
+}