refactor observer pattern

src/patterns/behavioral/observer.md

@@ -4,28 +4,12 @@ The Observer pattern is a behavioral design pattern where an object (the subject
 
 ### Step-by-Step Plan
 
-1- **Define the Observer trait**: Create a trait that observers must implement.
+1- **Define the Observer trait**: Create a trait that observers must implement.<br/>
+2- **Define the Subject struct**: Create a struct that maintains a list of observers and notifies them of changes.<br/>
+3- **Implement the Observer trait for concrete observers**: Create concrete observer structs that implement the Observer trait.<br/>
+4- **Demonstrate the Observer pattern in the main function**: Create a subject, add observers, and notify them of changes.<br/>
 
-```rust,noplaypen
-{{#include observer/src/observer.rs}}
-```
-
-2- **Define the Subject struct**: Create a struct that maintains a list of observers and notifies them of changes.
-
-```rust,noplaypen
-{{#include observer/src/subject.rs}}
-```
-
-3- **Implement the Observer trait for concrete observers**: Create concrete observer structs that implement the Observer trait.
-
-```rust,noplaypen
-{{#include observer/src/concrete_observer.rs}}
-```
-
-4- **Demonstrate the Observer pattern in the main function**: Create a subject, add observers, and notify them of changes.
-
-```rust,noplaypen
+```rust
 {{#include observer/src/main.rs}}
 ```
 
-You may find the sample project [here](https://github.com/saltukalakus/idiomatic-rust-snippets/tree/main/src/patterns/behavioral/observer).

src/patterns/behavioral/observer/src/main.rs

@@ -1,9 +1,49 @@
-mod observer;
-mod subject;
-mod concrete_observer;
+// Observer type
+pub trait Observer {
+    fn update(&self, message: &str);
+}
 
-use subject::Subject;
-use concrete_observer::ConcreteObserver;
+// Concrete observer
+pub struct ConcreteObserver {
+    name: String,
+}
+
+impl ConcreteObserver {
+    pub fn new(name: &str) -> Self {
+        ConcreteObserver {
+            name: name.to_string(),
+        }
+    }
+}
+
+impl Observer for ConcreteObserver {
+    fn update(&self, message: &str) {
+        println!("{} received message: {}", self.name, message);
+    }
+}
+
+// Subject
+pub struct Subject {
+    observers: Vec<Box<dyn Observer>>,
+}
+
+impl Subject {
+    pub fn new() -> Self {
+        Subject {
+            observers: Vec::new(),
+        }
+    }
+
+    pub fn add_observer(&mut self, observer: Box<dyn Observer>) {
+        self.observers.push(observer);
+    }
+
+    pub fn notify_observers(&self, message: &str) {
+        for observer in &self.observers {
+            observer.update(message);
+        }
+    }
+}
 
 fn main() {
     let mut subject = Subject::new();