piware.de Git - learn-rust.git/blobdiff - concepts/src/lib.rs projects / learn-rust.git / blobdiff commit grep author committer pickaxe ? search: re summary | shortlog | log | commit | commitdiff | tree raw | inline | side by side 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 ca0624142dea4d751e4506184bf84508de7e0696..5f1feea9404c8116e1cbb1106b825e5a6d52c677 100644 (file) --- 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} + } +} Learning Rust RSS Atom