struct Point { x: u64, y: u64, } enum Message { Resize { width: u64, height: u64 }, Move(Point), Echo(String), ChangeColor(u8, u8, u8), Quit, } struct State { width: u64, height: u64, position: Point, message: String, color: (u8, u8, u8), quit: bool, } impl State { fn resize(&mut self, width: u64, height: u64) { self.width = width; self.height = height; } fn move_position(&mut self, point: Point) { self.position = point; } fn echo(&mut self, s: String) { self.message = s; } fn change_color(&mut self, red: u8, green: u8, blue: u8) { self.color = (red, green, blue); } fn quit(&mut self) { self.quit = true; } fn process(&mut self, message: Message) { match message { Message::Resize { width, height } => self.resize(width, height), Message::Move(point) => self.move_position(point), Message::Echo(string) => self.echo(string), Message::ChangeColor(red, green, blue) => self.change_color(red, green, blue), Message::Quit => self.quit(), } } } fn main() { // You can optionally experiment here. } #[cfg(test)] mod tests { use super::*; #[test] fn test_match_message_call() { let mut state = State { width: 0, height: 0, position: Point { x: 0, y: 0 }, message: String::from("hello world"), color: (0, 0, 0), quit: false, }; state.process(Message::Resize { width: 10, height: 30, }); state.process(Message::Move(Point { x: 10, y: 15 })); state.process(Message::Echo(String::from("Hello world!"))); state.process(Message::ChangeColor(255, 0, 255)); state.process(Message::Quit); assert_eq!(state.width, 10); assert_eq!(state.height, 30); assert_eq!(state.position.x, 10); assert_eq!(state.position.y, 15); assert_eq!(state.message, "Hello world!"); assert_eq!(state.color, (255, 0, 255)); assert!(state.quit); } }

Defining an enum