add methods.md

solutions/method.md

@@ -0,0 +1,140 @@
+1.
+```rust
+struct Rectangle {
+    width: u32,
+    height: u32,
+}
+
+impl Rectangle {
+    fn area(&self) -> u32 {
+        self.width * self.height
+    }
+}
+
+fn main() {
+    let rect1 = Rectangle { width: 30, height: 50 };
+
+    assert_eq!(rect1.area(), 1500);
+}
+```
+
+2.
+```rust
+#[derive(Debug)]
+struct TrafficLight {
+    color: String,
+}
+
+impl TrafficLight {
+    pub fn show_state(&self)  {
+        println!("the current state is {}", self.color);
+    }
+}
+fn main() {
+    let light = TrafficLight{
+        color: "red".to_owned(),
+    };
+    // Don't take the ownership of `light` here
+    light.show_state();
+    // ..otherwise, there will be an error below
+    println!("{:?}", light);
+}
+```
+
+3.
+```rust
+struct TrafficLight {
+    color: String,
+}
+
+impl TrafficLight {
+    // using `Self` to fill in the blank
+    pub fn show_state(self: &Self)  {
+        println!("the current state is {}", self.color);
+    }
+
+    // fill in the blank, DON'T use any variants of `Self`
+    pub fn change_state(&mut self) {
+        self.color = "green".to_string()
+    }
+}
+fn main() {}
+```
+
+4.
+```rust
+#[derive(Debug)]
+struct TrafficLight {
+    color: String,
+}
+
+impl TrafficLight {
+    // 1. implement a assotiated function `new`,
+    // 2. it will return a TrafficLight contains color "red"
+    // 3. must use `Self`, DONT use `TrafficLight`
+    pub fn new() -> Self {
+        Self {
+            color: "red".to_string()
+        }
+    }
+
+    pub fn get_state(&self) -> &str {
+        &self.color
+    }
+}
+fn main() {
+    let light = TrafficLight::new();
+    assert_eq!(light.get_state(), "red");
+}
+```
+
+5.
+```rust
+struct Rectangle {
+    width: u32,
+    height: u32,
+}
+
+// rewrite Rectangle to use multiple `impl` blocks
+impl Rectangle {
+    fn area(&self) -> u32 {
+        self.width * self.height
+    }
+}
+
+impl Rectangle {
+    fn can_hold(&self, other: &Rectangle) -> bool {
+        self.width > other.width && self.height > other.height
+    }
+}
+fn main() {}
+```
+
+6.
+```rust
+#[derive(Debug)]
+enum TrafficLightColor {
+    Red,
+    Yellow,
+    Green,
+}
+
+// implement TrafficLightColor with a method
+impl TrafficLightColor {
+    fn color(&self) -> String {
+        match *self {
+            TrafficLightColor::Red => "red".to_string(),
+            TrafficLightColor::Yellow => "yellow".to_string(),
+            TrafficLightColor::Green => "green".to_string(),
+        }
+    }
+}
+
+fn main() {
+    let c = TrafficLightColor::Yellow;
+
+    assert_eq!(c.color(), "yellow");
+
+    println!("{:?}",c);
+}
+```

src/SUMMARY.md

@@ -21,7 +21,7 @@
 - [Pattern Match](pattern-match/intro.md)
   - [match, matches! and if let](pattern-match/match-iflet.md)
   - [Patterns](pattern-match/patterns.md)
-- [Method todo](method.md)
+- [Associated function & Method](method.md)
 - [Generics and Traits todo](generics-traits/intro.md)
   - [Generics](generics-traits/generics.md)
   - [Traits](generics-traits/traits.md)

src/method.md

@@ -1 +1,262 @@
-# Method
+# Associated function & Method
+
+## Examples
+```rust,editable
+struct Point {
+    x: f64,
+    y: f64,
+}
+
+// Implementation block, all `Point` associated functions & methods go in here
+impl Point {
+    // This is an "associated function" because this function is associated with
+    // a particular type, that is, Point.
+    //
+    // Associated functions don't need to be called with an instance.
+    // These functions are generally used like constructors.
+    fn origin() -> Point {
+        Point { x: 0.0, y: 0.0 }
+    }
+
+    // Another associated function, taking two arguments:
+    fn new(x: f64, y: f64) -> Point {
+        Point { x: x, y: y }
+    }
+}
+
+struct Rectangle {
+    p1: Point,
+    p2: Point,
+}
+
+impl Rectangle {
+    // This is a method
+    // `&self` is sugar for `self: &Self`, where `Self` is the type of the
+    // caller object. In this case `Self` = `Rectangle`
+    fn area(&self) -> f64 {
+        // `self` gives access to the struct fields via the dot operator
+        let Point { x: x1, y: y1 } = self.p1;
+        let Point { x: x2, y: y2 } = self.p2;
+
+        // `abs` is a `f64` method that returns the absolute value of the
+        // caller
+        ((x1 - x2) * (y1 - y2)).abs()
+    }
+
+    fn perimeter(&self) -> f64 {
+        let Point { x: x1, y: y1 } = self.p1;
+        let Point { x: x2, y: y2 } = self.p2;
+
+        2.0 * ((x1 - x2).abs() + (y1 - y2).abs())
+    }
+
+    // This method requires the caller object to be mutable
+    // `&mut self` desugars to `self: &mut Self`
+    fn translate(&mut self, x: f64, y: f64) {
+        self.p1.x += x;
+        self.p2.x += x;
+
+        self.p1.y += y;
+        self.p2.y += y;
+    }
+}
+
+// `Pair` owns resources: two heap allocated integers
+struct Pair(Box<i32>, Box<i32>);
+
+impl Pair {
+    // This method "consumes" the resources of the caller object
+    // `self` desugars to `self: Self`
+    fn destroy(self) {
+        // Destructure `self`
+        let Pair(first, second) = self;
+
+        println!("Destroying Pair({}, {})", first, second);
+
+        // `first` and `second` go out of scope and get freed
+    }
+}
+
+fn main() {
+    let rectangle = Rectangle {
+        // Associated functions are called using double colons
+        p1: Point::origin(),
+        p2: Point::new(3.0, 4.0),
+    };
+
+    // Methods are called using the dot operator
+    // Note that the first argument `&self` is implicitly passed, i.e.
+    // `rectangle.perimeter()` === `Rectangle::perimeter(&rectangle)`
+    println!("Rectangle perimeter: {}", rectangle.perimeter());
+    println!("Rectangle area: {}", rectangle.area());
+
+    let mut square = Rectangle {
+        p1: Point::origin(),
+        p2: Point::new(1.0, 1.0),
+    };
+
+    // Error! `rectangle` is immutable, but this method requires a mutable
+    // object
+    //rectangle.translate(1.0, 0.0);
+    // TODO ^ Try uncommenting this line
+
+    // Okay! Mutable objects can call mutable methods
+    square.translate(1.0, 1.0);
+
+    let pair = Pair(Box::new(1), Box::new(2));
+
+    pair.destroy();
+
+    // Error! Previous `destroy` call "consumed" `pair`
+    //pair.destroy();
+    // TODO ^ Try uncommenting this line
+}
+```
+
+## Exercises
+
+### Method
+1. 🌟🌟 Methods are similar to functions: declare with `fn`, have parameters and a return value.  Unlike functions, methods are defined within the context of a struct (or an enum or a trait object), and their first parameter is always `self`, which represents the instance of the struct the method is being called on.
+```rust,editable
+struct Rectangle {
+    width: u32,
+    height: u32,
+}
+
+impl Rectangle {
+    // complete the area method which return the area of a Rectangle
+    fn area
+}
+
+fn main() {
+    let rect1 = Rectangle { width: 30, height: 50 };
+
+    assert_eq!(rect1.area(), 1500);
+}
+```
+
+2. 🌟🌟 `self` will take the ownership of current struct instance, however, `&self` will only borrow a reference from the instance
+
+```rust,editable
+// Only fill in the blanks, DON'T remove any line!
+#[derive(Debug)]
+struct TrafficLight {
+    color: String,
+}
+
+impl TrafficLight {
+    pub fn show_state(__)  {
+        println!("the current state is {}", __.color);
+    }
+}
+fn main() {
+    let light = TrafficLight{
+        color: "red".to_owned(),
+    };
+    // Don't take the ownership of `light` here
+    light.show_state();
+    // ..otherwise, there will be an error below
+    println!("{:?}", light);
+}
+```
+3. 🌟🌟 The `&self` is actually short for `self: &Self`. Within an `impl` block, the type `Self` is an alias for the type that the `impl` block is for. Methods must have a parameter named `self` of type `Self` for their first parameter, so Rust lets you abbreviate this with only the name `self` in the first parameter spot. 
+```rust,editable
+struct TrafficLight {
+    color: String,
+}
+
+impl TrafficLight {
+    // using `Self` to fill in the blank
+    pub fn show_state(__)  {
+        println!("the current state is {}", self.color);
+    }
+
+    // fill in the blank, DON'T use any variants of `Self`
+    pub fn change_state() {
+        self.color = "green".to_string()
+    }
+}
+fn main() {}
+```
+
+
+### Associated function
+
+4. 🌟🌟  All functions defined within an `impl` block are called associated functions because they’re associated with the type named after the `impl`. We can define associated functions that don’t have `self` as their first parameter (and thus are not methods) because they don’t need an instance of the type to work with.
+
+```rust,editable
+#[derive(Debug)]
+struct TrafficLight {
+    color: String,
+}
+
+impl TrafficLight {
+    // 1. implement a assotiated function `new`,
+    // 2. it will return a TrafficLight contains color "red"
+    // 3. must use `Self`, DONT use `TrafficLight`
+    pub fn new() 
+
+    pub fn get_state(&self) -> &str {
+        &self.color
+    }
+}
+
+fn main() {
+    let light = TrafficLight::new();
+    assert_eq!(light.get_state(), "red");
+}
+```
+
+### Multiple `impl` blocks
+5. 🌟 Each struct is allowed to have multiple impl blocks. 
+```rust,editable
+
+struct Rectangle {
+    width: u32,
+    height: u32,
+}
+
+// rewrite Rectangle to use multiple `impl` blocks
+impl Rectangle {
+    fn area(&self) -> u32 {
+        self.width * self.height
+    }
+
+    fn can_hold(&self, other: &Rectangle) -> bool {
+        self.width > other.width && self.height > other.height
+    }
+}
+
+
+fn main() {}
+```
+
+### Enums
+6. 🌟🌟🌟 We can also implement methods for enums.
+
+```rust,editable
+
+#[derive(Debug)]
+enum TrafficLightColor {
+    Red,
+    Yellow,
+    Green,
+}
+
+// implement TrafficLightColor with a method
+impl TrafficLightColor {
+    
+}
+
+fn main() {
+    let c = TrafficLightColor::Yellow;
+
+    assert_eq!(c.color(), "yellow");
+
+    println!("{:?}",c);
+}
+```
+
+## Practice
+
+@todo