===========
Using Bases
===========
While the :class:`~clap.command.Command` is what wraps the main logic of your
program, Bases are responsible for parsing options, providing help, and
actually running the commands.


.. currentmodule:: clap.base

Single-Command Base
===================
If your program does not need multiple subcommands, you can just use a
:class:`SingleBase`. It does not require as much configuration as a
:class:`MultiBase`, as it gets most of its information from its
:class:`~clap.command.Command`.

.. autoclass:: SingleBase
   :members:

Often, using a :class:`SingleBase` to run your command is as simple as::

    if __name__ == '__main__':
        base = SingleBase(CommandClass)
        base.run()


Multi-Command Base
==================
On the other hand, multiple-subcommand programs along the lines of hg or svn
need the :class:`MultiBase`.

.. autoclass:: MultiBase
   :members:

However, it is often better to create your own subclass of :class:`MultiBase`
to use in your application. For example, the "todo.py" demo application uses
this code for its base::

    class TodoBase(MultiBase):
        long_desc = """This is a simple to-do list manager. It uses a simple \
    text file, and you can mark tasks as high, normal, or low priority."""
        global_options = (
            Option('f', 'file', argument=True, desc="The to-do list file "
                   "(defaults to ~/.todolist"),
            Option('v', 'verbose', desc="Print more output than normal")
        )
        global_defaults = dict(
            file=os.path.expanduser('~/.todolist'),
            verbose=False
        )


The Base Class
==============
Both :class:`SingleBase` and :class:`MultiBase` are derived from a single
class, :class:`Base`. If you want to write a command-line application working
on completely different principles, you can subclass from this to gain some
useful utilities.

.. autoclass:: Base
   :members: