commad_pattern.rs

fn main() {
    let mut editor = Editor::new();
    let mut history = History::new();

    input("one", &mut editor, &mut history);
    input("_", &mut editor, &mut history);
    input("two", &mut editor, &mut history);

    undo_all(&mut editor, &mut history);
}

type Editor = String;
type History = Vec<Box<dyn Command>>;

fn input(text: &str, editor: &mut Editor, history: &mut History) {
    let mut command = InputText::new(text);

    println!("Execute InputText: '{}'", text);
    command.execute(editor);

    println!("editor: '{}'\n", editor);
    history.push(Box::new(command));
}

fn undo_all(editor: &mut Editor, history: &mut History) {
    for command in &mut history.iter_mut().rev() {
        println!("After Undo.");
        command.undo(editor);

        println!("editor: '{}'\n", editor);
    }
}


trait Command {
    fn execute(&mut self, editor: &mut Editor);
    fn undo(&mut self, _editor: &mut Editor) {}
    fn is_save_history(&self) -> bool { false }
}

struct InputText {
    text: String,
    position: Option<usize>,
}

impl InputText {
    fn new(text: &str) -> Self {
        Self {
            text: text.to_string(),
            position: None,
        }
    }
}

impl Command for InputText {
    fn execute(&mut self, editor: &mut Editor) {
        if self.position != None {
            return;
        }

        self.position = Some(editor.len());
        editor.push_str(&self.text);
    }

    fn undo(&mut self, editor: &mut Editor) {
        if let Some(start) = self.position {
            let end = start + self.text.len();
            editor.replace_range(start..end, "");
        }
    }

    fn is_save_history(&self) -> bool { true }
}