Example with references and mutable references

src/main.rs

@@ -1,4 +1,4 @@
-#[derive(Copy, Clone)]
+//#[derive(Copy, Clone)]
 struct RGB {
     red: u8,
     green: u8,
@@ -11,19 +11,11 @@ impl RGB {
     }
 
     fn black() -> RGB {
-        RGB {
-            red: 0,
-            green: 0,
-            blue: 0,
-        }
+        RGB::new(0, 0, 0)
     }
 
     fn white() -> RGB {
-        RGB {
-            red: 255,
-            green: 255,
-            blue: 255,
-        }
+        RGB::new(255, 255, 255)
     }
 }
 
@@ -58,13 +50,27 @@ impl Image {
         Image::new(width, height, data)
     }
 
-    fn get(&self, x: usize, y: usize) -> RGB {
-        self.data[y * self.width + x]
+    fn get(&self, x: usize, y: usize) -> &RGB {
+        self.data.get(y * self.width + x).unwrap()
+    }
+
+    fn get_mut(&mut self, x: usize, y: usize) -> &mut RGB {
+        self.data.get_mut(y * self.width + x).unwrap()
     }
 }
 
+fn manipulate_first_pixel(image: &mut Image) {
+    let c = image.get_mut(0, 0);
+
+    c.red = 0;
+}
+
 fn main() {
-    let image = Image::white_image(640, 480);
+    let mut image = Image::white_image(640, 480);
+
+    manipulate_first_pixel(&mut image);
 
     let c = image.get(0, 0);
+
+    println!("red = {}, green = {}, blue = {}", c.red, c.green, c.blue)
 }