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.. _qml-chapter2-methods:
Extending QML - Connecting to C++ Methods and Signals
=====================================================
This is the second of a series of 6 examples forming a tutorial about extending
QML with Python.
Suppose we want ``PieChart`` to have a ``clearChart()`` method that erases the
chart and then emits a ``chartCleared`` signal. Our ``app.qml`` would be able
to call ``clearChart()`` and receive ``chartCleared()`` signals like this:
.. literalinclude:: app.qml
:lineno-start: 4
:lines: 4-32
To do this, we add a ``clearChart()`` method and a ``chartCleared()`` signal
to our C++ class:
.. literalinclude:: methods.py
:lineno-start: 54
:lines: 54-58
The use of the ``Slot`` decorator makes the ``clearChart()`` method available
to the Qt Meta-Object system, and in turn, to QML. The method simply changes
the color to ``Qt::transparent``, repaints the chart, then emits the
``chartCleared()`` signal:
.. literalinclude:: methods.py
:lineno-start: 21
:lines: 21-24
Now when we run the application and click the window, the pie chart disappears,
and the application outputs::
qml: The chart has been cleared
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