Vala interface madness
######################

:date: 2016-02-26T13:07:52Z
:category: blog
:tags: vala,development
:url: 2016/02/26/vala-interface-madness/
:save_as: 2016/02/26/vala-interface-madness/index.html
:status: published
:author: "Gergely Polonkai"

Although I have just started making it in C, I decided to move my Matrix GLib SDK to Vala.  First
to learn a new language, and second because it is much easier to write GObject based stuff with
it.

For the first step I created a ``.vapi`` file from my existing sources, so the whole SDK prototype
was available for me in Vala.

I had a ``MatrixEvent`` class that implemented the ``GInitable`` interface, and many others were
subclassed ``MatrixEvent``.  For some reason I don’t remember, I created the following header for
one of the event classes:

.. code-block:: vala

   public class MatrixPresenceEvent : GLib.Object, GLib.Initable {

This is nice and everything, but as I didn’t create an ``init()`` method for
``MatrixPresenceEvent``, it tried to use the one from the parent class and somehow got into an
infinite loop.  The Vala transformer (``valac``), however, doesn’t mention this.

Lessons learned: if you implement an interface on a subclass that is implemented by the parent
don’t forget to add the necessary functions to the subclass.