=============
Class: Simple
=============

.. index:: template for authors

.. |a| image:: /images/all/blender-extended/class-100.png

Objectives
==========
   
.. tabularcolumns:: | c | l |
   :border: none

+-------+-------------------------------------------------------------------------+
|  |a|  | Classes are part of a programming paradigma. We use Python which is  a  |  
|       | object oriented programming language,                                   |
|       | With this knowledge it is possible to build and add new functionality   | 
|       | to Blender and your projects. Let's see how it works.                   |
+-------+-------------------------------------------------------------------------+

Instructions
============
:Tasks:

1. Read the text about objectoriented programming on wikipedia. 
2. Build and test the class shown in this station.
3. Replace the text with your own.
4. Mix the concept of a class with positioning a Text in the 3D-View 
   (:ref:`Text in 3D <text_in_3d_view>`).

Simple class
============
This example is taken from:  `Blender API <http://www.blender.org/documentation/blender_python_api_2_67_1/bpy.types.Operator.html#basic-operator-example>`_.

The code:

.. literalinclude:: files/simple_class.py
   :language: python

Notes about the code (step by step)
===================================
A class definition is introduced by the keyword class, followed by a self-selected name and finally a pair of parentheses. As in our case, the class can also inherit properties of another class, in our example *bpy.types.Operator*. A colon marks the start of the block, the next line(s) must be indented.

.. literalinclude:: files/simple_class.py
   :language: python
   :lines: 4
   
Two variables are defined that. This ist necessary for the integration of our class in the Blender system.

.. literalinclude:: files/simple_class.py
   :language: python
   :lines: 5, 6

No class without methods. A method is introduced by the keyword *def* and the first parameter used, is *self*. With *self* the connection between function and class is defined. In our example, the second parameter *context* is mandatory and  used by Blender. The function does not really do much. Finally a typical blender statement, gives  the value *{'FINISHED'}* back.

.. literalinclude:: files/simple_class.py
   :language: python
   :lines: 8-11

Finally, the new class is registered in the Blender system and also a trial statement is called. The result can be seen in the console. There, the *Hello World* should be printed as expected.


.. literalinclude:: files/simple_class.py
   :language: python
   :lines: 11-15