#02-ExtensionMethods

Author: defuncart

#02-ExtensionMethods/README.md

@@ -0,0 +1,45 @@
+# 02 - Extension Methods
+
+*Extension Methods* allow us to add functionality to existing classes. Say for instance we want to set the X position of a Transform. We could write a private method within our class MyGameObject but as this is probably something that we could use across multiple classes, it makes more sense to create an Extension Method
+
+```C#
+public static void SetX(this Transform transform, float x)
+{
+  Vector3 position = transform.position;
+  position.x = x;
+  transform.position = position;
+}
+```
+
+which can be called on any Transform in any class.
+
+```C#
+Transform myTransform.
+myTransform.SetX(100);
+```
+
+As *transform.position* is a property and not a variable, Extension Methods like *SetX*, *SetY*, *MoveToInTime* etc. are extremely useful as they reduce duplicated lines of code, while making the code more understandable.
+
+One issue with Extension Methods is that there are no automatic null checks. So if myTransform happens to be null, then a **NullReferenceException** will be thrown when trying to call SetX. Thus we need to explicitly check for null, if applicable.
+
+```C#
+public static void SetX(this Transform transform, float x)
+{
+  if(transform == null) { Debug.LogError("transform is null"); return; }
+
+  Vector3 position = transform.position;
+  position.x = x;
+  transform.position = position;
+}
+```
+
+```C#
+public static bool IsNullOrEmpty(this string value)
+{
+  return string.IsNullOrEmpty(value);
+}
+```
+
+If you are unfamiliar with Extension Methods, then I suggest you take a look [here](https://msdn.microsoft.com/pl-pl/library/windows/desktop/bb383977(v=vs.100).aspx), [here](https://unity3d.com/learn/tutorials/topics/scripting/extension-methods) and [here](http://www.alanzucconi.com/2015/08/05/extension-methods-in-c/), and start utilizing them within your projects!
+
+Note that Extension Methods can be written inside any static class. Some developers like to have a single *ExtensionMethods.cs* file, others like to break the methods out into separate files, for instance *StringExtentions.cs*, *TransformExtensions.cs* etc.