+use std::collections::HashMap;
use std::fs::File;
use std::io::prelude::*;
-use std::collections::HashMap;
pub fn read_file(path: &str) -> Result<String, std::io::Error> {
let mut s = String::new();
- File::open(path)?
- .read_to_string(&mut s)?;
+ File::open(path)?.read_to_string(&mut s)?;
Ok(s)
}
V: Copy,
{
pub fn new(calc: T) -> Cacher<T, A, V> {
- Cacher { calc, values: HashMap::new() }
+ Cacher {
+ calc,
+ values: HashMap::new(),
+ }
}
pub fn value(&mut self, arg: A) -> V {
}
pub struct Counter5 {
- count: u32
+ count: u32,
}
impl Counter5 {
}
}
}
+
+pub struct Post {
+ state: Box<dyn State>,
+ content: String,
+}
+
+impl Post {
+ pub fn new() -> Post {
+ Post {
+ state: 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.content(self)
+ }
+
+ pub fn request_review(&mut self) {
+ self.state = self.state.request_review();
+ }
+
+ pub fn approve(&mut self) {
+ self.state = self.state.approve();
+ }
+
+ pub fn reject(&mut self) {
+ self.state = self.state.reject();
+ }
+}
+
+trait 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 {
+ ""
+ }
+}
+
+struct Draft {}
+impl State for Draft {
+ 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 reject(&self) -> Box<dyn State> {
+ Box::new(Self {})
+ }
+}
+
+struct PendingReview {
+ acks: u32,
+}
+
+impl State for PendingReview {
+ fn request_review(&self) -> Box<dyn State> {
+ Box::new(Self { acks: self.acks })
+ }
+
+ 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<dyn State> {
+ Box::new(Self {})
+ }
+
+ 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,
+ }
+ }
+}