study_example/object_oriented/
object_oriented_desgin_pattern.rs

1pub struct Post {
2    // 定义了不同帖子的不同状态
3    state: Option<Box<dyn State>>,
4    content: String,
5}
6
7impl Post {
8    pub fn new() -> Post {
9        Post {
10            state: Some(Box::new(Draft {})),
11            content: String::new(),
12        }
13    }
14    pub fn add_text(&mut self, text: &str) {
15        self.content.push_str(text);
16    }
17
18    pub fn content(&self) -> &str {
19        self.state.as_ref().unwrap().content(self)
20    }
21
22    pub fn request_review(&mut self) -> &mut Self {
23        if let Some(s) = self.state.take() {
24            self.state = Some(s.request_review())
25        }
26        self
27    }
28
29    pub fn approve(&mut self) -> &mut Self {
30        if let Some(s) = self.state.take() {
31            self.state = Some(s.approve())
32        }
33        self
34    }
35}
36
37trait State {
38    fn request_review(self: Box<Self>) -> Box<dyn State>;
39    fn approve(self: Box<Self>) -> Box<dyn State>;
40    fn content<'a>(&self, post: &'a Post) -> &'a str {
41        ""
42    }
43}
44
45struct Draft {}
46
47impl State for Draft {
48    fn request_review(self: Box<Self>) -> Box<dyn State> {
49        Box::new(PendingReview {})
50    }
51    fn approve(self: Box<Self>) -> Box<dyn State> {
52        self
53    }
54}
55
56struct PendingReview {}
57
58impl State for PendingReview {
59    fn request_review(self: Box<Self>) -> Box<dyn State> {
60        self
61    }
62    fn approve(self: Box<Self>) -> Box<dyn State> {
63        Box::new(Published {})
64    }
65}
66
67struct Published {}
68
69impl State for Published {
70    fn request_review(self: Box<Self>) -> Box<dyn State> {
71        self
72    }
73    fn approve(self: Box<Self>) -> Box<dyn State> {
74        self
75    }
76    fn content<'a>(&self, post: &'a Post) -> &'a str {
77        &post.content
78    }
79}
80
81pub fn object_oriented_desgin_pattern_study() {
82    let mut post = Post::new();
83    post.add_text("I ate a salad for lunch today");
84    let post = post.request_review();
85    let post = post.approve();
86    match &post.state {
87        None => println!("None"),
88        Some(state) => {
89            println!("state:")
90        }
91    }
92}
study_example/object_oriented/object_oriented_desgin_pattern.rs

study_example/object_oriented/
object_oriented_desgin_pattern.rs
