X-Git-Url: https://piware.de/gitweb/?p=learn-rust.git;a=blobdiff_plain;f=concepts%2Fsrc%2Flib.rs;h=5f1feea9404c8116e1cbb1106b825e5a6d52c677;hp=ca0624142dea4d751e4506184bf84508de7e0696;hb=d6fbfabfaf434ae365854f0587547cff3ca78dae;hpb=c182c6166ae3971320daaeadba3ea718124303e7;ds=sidebyside

diff --git a/concepts/src/lib.rs b/concepts/src/lib.rs
index ca06241..5f1feea 100644
--- a/concepts/src/lib.rs
+++ b/concepts/src/lib.rs
@@ -110,14 +110,14 @@ impl Iterator for Counter5 {
 }
 
 pub struct Post {
-    state: Option<Box<dyn State>>,
+    state: Box<dyn State>,
     content: String,
 }
 
 impl Post {
     pub fn new() -> Post {
         Post {
-            state: Some(Box::new(Draft {})),
+            state: Box::new(Draft {}),
             content: String::new(),
         }
     }
@@ -127,27 +127,26 @@ impl Post {
     }
 
     pub fn content(&self) -> &str {
-        // as_ref() converts Option<Box<State>> to Option<&Box<State>>
-        // state can never be None, all state transitions return a new one
-        self.state.as_ref().unwrap().content(self)
+        self.state.content(self)
     }
 
     pub fn request_review(&mut self) {
-        if let Some(s) = self.state.take() {
-            self.state = Some(s.request_review());
-        }
+        self.state = self.state.request_review();
     }
 
     pub fn approve(&mut self) {
-        if let Some(s) = self.state.take() {
-            self.state = Some(s.approve());
-        }
+        self.state = self.state.approve();
+    }
+
+    pub fn reject(&mut self) {
+        self.state = self.state.reject();
     }
 }
 
 trait State {
-    fn request_review(self: Box::<Self>) -> Box<dyn State>;
-    fn approve(self: Box::<Self>) -> Box<dyn State>;
+    fn request_review(&self) -> Box<dyn State>;
+    fn approve(&mut self) -> Box<dyn State>;
+    fn reject(&self) -> Box<dyn State>;
 
     #[allow(unused_variables)]
     fn content<'a>(&self, post: &'a Post) -> &'a str {
@@ -157,37 +156,100 @@ trait State {
 
 struct Draft {}
 impl State for Draft {
-    fn request_review(self: Box::<Self>) -> Box<dyn State> {
-        Box::new(PendingReview {})
+    fn request_review(&self) -> Box<dyn State> {
+        Box::new(PendingReview {acks: 0})
+    }
+
+    fn approve(&mut self) -> Box<dyn State> {
+        // don't change state
+        Box::new(Self {})
     }
 
-    fn approve(self: Box::<Self>) -> Box<dyn State> {
-        self
+    fn reject(&self) -> Box<dyn State> {
+        Box::new(Self {})
     }
 }
 
-struct PendingReview {}
+struct PendingReview {
+    acks: u32,
+}
+
 impl State for PendingReview {
-    fn request_review(self: Box::<Self>) -> Box<dyn State> {
-        self
+    fn request_review(&self) -> Box<dyn State> {
+        Box::new(Self {acks: self.acks})
     }
 
-    fn approve(self: Box::<Self>) -> Box<dyn State> {
-        Box::new(Published {})
+    fn approve(&mut self) -> Box<dyn State> {
+        if self.acks >= 1 {
+            Box::new(Published {})
+        } else {
+            Box::new(Self {acks: self.acks + 1})
+        }
+    }
+
+    fn reject(&self) -> Box<dyn State> {
+        Box::new(Draft {})
     }
 }
 
 struct Published {}
 impl State for Published {
-    fn request_review(self: Box::<Self>) -> Box<dyn State> {
-        self
+    fn request_review(&self) -> Box<dyn State> {
+        Box::new(Self {})
     }
 
-    fn approve(self: Box::<Self>) -> Box<dyn State> {
+    fn approve(&mut self) -> Box<dyn State> {
         Box::new(Published {})
     }
 
+    fn reject(&self) -> Box<dyn State> {
+        Box::new(Self {})
+    }
+
     fn content<'a>(&self, post: &'a Post) -> &'a str {
         &post.content
     }
 }
+
+// state encoded as types; this is the "approved" state
+pub struct TPost {
+    content: String,
+}
+
+impl TPost {
+    pub fn new() -> TPostDraft {
+        TPostDraft {content: String::new()}
+    }
+
+    pub fn content(&self) -> &str {
+        &self.content
+    }
+}
+
+pub struct TPostDraft {
+    content: String,
+}
+
+impl TPostDraft {
+    pub fn add_text(&mut self, text: &str) {
+        self.content.push_str(text);
+    }
+
+    pub fn request_review(self) -> TPostReview {
+        TPostReview {content: self.content}
+    }
+}
+
+pub struct TPostReview {
+    content: String,
+}
+
+impl TPostReview {
+    pub fn approve(self) -> TPost {
+        TPost {content: self.content}
+    }
+
+    pub fn reject(self) -> TPostDraft {
+        TPostDraft {content: self.content}
+    }
+}