From 2f1050e854dcc0331c84d2f4879f849bd9f14cdf Mon Sep 17 00:00:00 2001
From: laurens <miers132@gmail.com>
Date: Sun, 11 Oct 2020 15:28:09 +0200
Subject: [PATCH] Add state pattern: OOP-way

---
 state_pattern_oop/Cargo.toml  |  9 ++++
 state_pattern_oop/src/main.rs | 95 +++++++++++++++++++++++++++++++++++
 2 files changed, 104 insertions(+)
 create mode 100644 state_pattern_oop/Cargo.toml
 create mode 100644 state_pattern_oop/src/main.rs

diff --git a/state_pattern_oop/Cargo.toml b/state_pattern_oop/Cargo.toml
new file mode 100644
index 0000000..1992881
--- /dev/null
+++ b/state_pattern_oop/Cargo.toml
@@ -0,0 +1,9 @@
+[package]
+name = "state_pattern_oop"
+version = "0.1.0"
+authors = ["laurens <miers132@gmail.com>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
diff --git a/state_pattern_oop/src/main.rs b/state_pattern_oop/src/main.rs
new file mode 100644
index 0000000..b8dfa55
--- /dev/null
+++ b/state_pattern_oop/src/main.rs
@@ -0,0 +1,95 @@
+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 {
+        self.state.as_ref().unwrap().content(self)
+    }
+
+    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<dyn State>;
+    fn approve(self: Box<Self>) -> Box<dyn State>;
+
+    fn content<'a>(&self, _post: &'a Post) -> &'a str {
+        ""
+    }
+}
+
+struct Draft {}
+
+impl State for Draft {
+    fn request_review(self: Box<Self>) -> Box<dyn State> {
+        Box::new(PendingReview {})
+    }
+
+    fn approve(self: Box<Self>) -> Box<dyn State> {
+        self
+    }
+}
+
+struct PendingReview {}
+
+impl State for PendingReview {
+    fn request_review(self: Box<Self>) -> Box<dyn State> {
+        self
+    }
+
+    fn approve(self: Box<Self>) -> Box<dyn State> {
+        Box::new(Published {})
+    }
+}
+
+struct Published {}
+
+impl State for Published {
+    fn request_review(self: Box<Self>) -> Box<dyn State> {
+        self
+    }
+
+    fn approve(self: Box<Self>) -> Box<dyn State> {
+        self
+    }
+
+    fn content<'a>(&self, post: &'a Post) -> &'a str {
+        &post.content
+    }
+}
+
+fn main() {
+    let mut post = Post::new();
+
+    post.add_text("I ate a salad for lunch today");
+    assert_eq!("", post.content());
+
+    post.request_review();
+    assert_eq!("", post.content());
+
+    post.approve();
+    assert_eq!("I ate a salad for lunch today", post.content());
+}