div></div><div class="field "><a name="once"></a><h3><p><code><a href="#once"><span class="identifier">once</span></a> (<span style="white-space:nowrap">event:<a class="type" title="The basic String class." href="../String.html">String</a>,</span> <span style="white-space:nowrap">fn:<a class="type" title="The EventCallback class holds the callback function It also make both the callback and it's arguments accessible and assignable  	from the class instance." href="../fbp/EventCallback.html">EventCallback</a