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Update blog example to use types to enforce state

This commit is contained in:
Timothy Warren 2019-02-06 15:02:36 -05:00
parent 48e6aba776
commit 36ed658b19
4 changed files with 48 additions and 119 deletions
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73
.idea/workspace.xml
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@ -2,9 +2,8 @@
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<change beforePath="$PROJECT_DIR$/blog/src/lib.rs" beforeDir="false" afterPath="$PROJECT_DIR$/blog/src/lib.rs" afterDir="false" />
<change beforePath="$PROJECT_DIR$/blog/src/main.rs" beforeDir="false" afterPath="$PROJECT_DIR$/blog/src/main.rs" afterDir="false" />
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<option name="EXCLUDED_CONVERTED_TO_IGNORED" value="true" />
<option name="SHOW_DIALOG" value="false" />
@ -17,8 +16,8 @@
<file pinned="false" current-in-tab="true">
<entry file="file://$PROJECT_DIR$/blog/src/main.rs">
<provider selected="true" editor-type-id="text-editor">
<state relative-caret-position="224">
<caret line="14" lean-forward="true" selection-start-line="14" selection-end-line="14" />
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</state>
</provider>
</entry>
@ -26,29 +25,13 @@
<file pinned="false" current-in-tab="false">
<entry file="file://$PROJECT_DIR$/blog/src/lib.rs">
<provider selected="true" editor-type-id="text-editor">
<state relative-caret-position="624">
<caret line="39" column="5" lean-forward="true" selection-start-line="39" selection-start-column="5" selection-end-line="39" selection-end-column="5" />
<state relative-caret-position="672">
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@ -132,8 +115,8 @@
<option value="$PROJECT_DIR$/trait_objects/Cargo.toml" />
<option value="$PROJECT_DIR$/gui/src/main.rs" />
<option value="$PROJECT_DIR$/gui/src/lib.rs" />
<option value="$PROJECT_DIR$/blog/src/main.rs" />
<option value="$PROJECT_DIR$/blog/src/lib.rs" />
<option value="$PROJECT_DIR$/blog/src/main.rs" />
</list>
</option>
</component>
@ -217,7 +200,7 @@
</component>
<component name="PropertiesComponent">
<property name="JavaScriptWeakerCompletionTypeGuess" value="true" />
<property name="com.android.tools.idea.instantapp.provision.ProvisionBeforeRunTaskProvider.myTimeStamp" value="1549482664512" />
<property name="com.android.tools.idea.instantapp.provision.ProvisionBeforeRunTaskProvider.myTimeStamp" value="1549483257467" />
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<property name="js.eslint.eslintPackage" value="$USER_HOME$/.yarn-config/global/node_modules/.bin/eslint" />
<property name="js.eslint.nodeInterpreter" value="project" />
@ -822,37 +805,21 @@
</entry>
<entry file="file://$PROJECT_DIR$/blog/src/lib.rs">
<provider selected="true" editor-type-id="text-editor">
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<entry file="file://$PROJECT_DIR$/blog/src/main.rs">
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</state>
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</entry>

2
blog/Cargo.toml
View File

@ -1,6 +1,6 @@
[package]
name = "blog"
version = "0.1.0"
version = "0.2.0"
authors = ["Timothy Warren <twarren@nabancard.com>"]
edition = "2018"

85
blog/src/lib.rs
View File

@ -1,81 +1,44 @@
pub struct Post {
state: Option<Box<dyn State>>,
content: String,
}
pub struct DraftPost {
content: String,
}
impl Post {
pub fn new() -> Post {
Post {
state: Some(Box::new(Draft {})),
pub fn new() -> DraftPost {
DraftPost {
content: String::new(),
}
}
pub fn content(&self) -> &str {
&self.content
}
}
impl DraftPost {
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())
pub fn request_review(self) -> PendingReviewPost {
PendingReviewPost {
content: self.content,
}
}
}
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 {
""
pub struct PendingReviewPost {
content: String,
}
impl PendingReviewPost {
pub fn approve(self) -> Post {
Post {
content: self.content,
}
}
}
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
}
}

7
blog/src/main.rs
View File

@ -4,11 +4,10 @@ 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());
let post = post.request_review();
let post = post.approve();
post.approve();
assert_eq!("I ate a salad for lunch today", post.content());
}