pub struct Post {
    state: Option<Box<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())
        }
    }

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

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

struct Draft {}

impl State for Draft {
    fn request_review(self: Box<Self>) -> Box<State> {
        Box::new(PendingReview {})
    }
}

struct PendingReview {}

impl State for PendingReview {
    fn request_review(&self: Box<Self>) -> Box<State> {
        self
    }
}

pub struct Post {
    state: Option<Box<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<State>;
}

struct Draft {}

impl State for Draft {
    fn request_review(self: Box<Self>) -> Box<State> {
        Box::new(PendingReview {})
    }
}

struct PendingReview {}

impl State for PendingReview {
    fn request_review(&self: Box<Self>) -> Box<State> {
        self
    }
}

--- 
+++ 
@@ -24,6 +24,12 @@
             self.state = Some(s.request_review())
         }
     }
+
+    pub fn approve(&mut self) {
+        if let Some(s) = self.state.take() {
+            self.state = Some(s.approve())
+        }
+    }
 }
 
 trait State {
Implement method approve on post
