concepts: Add alternative Post implementation with states as types

[learn-rust.git] / concepts / src / lib.rs

diff --git a/concepts/src/lib.rs b/concepts/src/lib.rs
index b0839ad391739cb186adcf2bb81c97484c5a3dfe..5f1feea9404c8116e1cbb1106b825e5a6d52c677 100644 (file)
--- a/concepts/src/lib.rs
+++ b/concepts/src/lib.rs
@@ -210,3 +210,46 @@ impl State for Published {
         &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}
+    }
+}