小编Moh*_*adi的帖子

在这段代码中：

pub struct Post {
    state: Option<Box<dyn State>>,
    content: String,
}

impl Post {
    pub fn new() -> Post {
        Post {
            state: Some(Box::new(Draft {})),
            content: String::new(),
        }
    }
    
    pub fn add_text(&mut self, text: &str) {
        self.content.push_str(text);
    }
    
    pub fn content(&self) -> &str {
        ""
    }

    pub fn request_review(&mut self) {
        if let Some(s) = self.state.take() {
            self.state = Some(s.request_review())
        }
    }
}

trait State {
    fn request_review(self: Box<Self>) -> Box<dyn State>; 
}

struct Draft {}

impl State for Draft …