onto struct ex

data_types.md

@@ -419,4 +419,38 @@ This still holds values in the field
 
     let black = RGBColour(0, 0, 0);
     let origin = Point(0, 0, 0);
-```
+```
+
+## Unit Like Struct
+
+This is similar to a unit ()
+This holds no data in itself
+
+Useful for when you need to implement a trait on some type but dont want to store data in the type itself
+
+Delcaration
+```rust
+struct unit_like_type;
+
+    let using_unit_like_struct = unit_like_type; // instance of unit_like_type
+```
+
+No need for () in the delcaration
+
+## Structure Ownership
+
+Want each instance of a struct to own the values inside so that the values inside are always valid unless specified
+
+Can use references but need to take advantage of lifetimes which ensures that the reference is valid whilst the structure is valid
+
+This is valid but compiler will ask for lifetime specifiers
+```rust
+struct User {
+    active: bool,
+    username: &str,
+    email: &str,
+    sign_in_count: u64,
+}
+```
+
+In short use data times that are owned rather than references