.. include:: <mmlalias.txt>


Adapter
=======

.. contents::
   :local:

Problem
-------

The sensor hierarchy of our company covers many different
sensors. However, management has decided that our repertoire is not
broad enough, and some sensors of another company need to be
added. That company has software implementations for those sensors
that we could technically use. Naturally, those software
implementations do not fit into our hierarchy [#impedance_mismatch]_.

What they have, though, is a similar hierarchy (one interface for all
their sensors), with the only apparent difference being that they
measure in degrees Fahrenheit instead.

.. plantuml::

   @startuml

   interface FahrenheitSensor {
     + get_temperature_f()
   }

   class ConstantFahrenheitSensor {
     + get_temperature_f()
   }
   class RandomFahrenheitSensor {
     + get_temperature_f()
   }

   FahrenheitSensor <|.. ConstantFahrenheitSensor
   FahrenheitSensor <|.. RandomFahrenheitSensor

   @enduml

.. literalinclude:: /trainings/material/soup/cxx/cxx-code/design-patterns-adapter/sensors-fahrenheit/sensor-fahrenheit.h
   :caption: :download:`/trainings/material/soup/cxx/cxx-code/design-patterns-adapter/sensors-fahrenheit/sensor-fahrenheit.h`
   :language: c++

Solution: Adaptation
--------------------

Seems like we could be able to integrate all of their sensors in one
swoop, *easily*.

.. plantuml::

   @startuml

   interface Sensor {
     + get_temperature()
   }
   class FahrenheitSensorAdapter {
     + get_temperature()
   }
   Sensor <|.. FahrenheitSensorAdapter
   FahrenheitSensorAdapter -r-> FahrenheitSensor

   interface FahrenheitSensor {
     + get_temperature_f()
   }
   class ConstantFahrenheitSensor {
     + get_temperature_f()
   }
   class RandomFahrenheitSensor {
     + get_temperature_f()
   }

   FahrenheitSensor <|.. ConstantFahrenheitSensor
   FahrenheitSensor <|.. RandomFahrenheitSensor

   @enduml

.. note::

   Convert Fahrenheit to Celsius using the following formula:

   .. math::

      C = (F - 32) * 5 / 9

Exercise
--------

Implement such an adapter class into our sensor hierarchy, such that
the following tests are satisfied. Implement one by one, and take your
time.

Basic Adaptation
................

.. literalinclude:: /trainings/material/soup/cxx/cxx-code/design-patterns-adapter/tests/adapter-suite-basic.cpp
   :caption: :download:`/trainings/material/soup/cxx/cxx-code/design-patterns-adapter/tests/adapter-suite-basic.cpp`
   :language: c++

Adapter Must *Be-A* ``Sensor``
..............................

.. literalinclude:: /trainings/material/soup/cxx/cxx-code/design-patterns-adapter/tests/adapter-suite-adapter--is-a--sensor.cpp
   :caption: :download:`/trainings/material/soup/cxx/cxx-code/design-patterns-adapter/tests/adapter-suite-adapter--is-a--sensor.cpp`
   :language: c++

Adaptee Can *Be-Any* ``ASensor``
................................

.. literalinclude:: /trainings/material/soup/cxx/cxx-code/design-patterns-adapter/tests/adapter-suite-adapter--knows--an-a-sensor.cpp
   :caption: :download:`/trainings/material/soup/cxx/cxx-code/design-patterns-adapter/tests/adapter-suite-adapter--knows--an-a-sensor.cpp`
   :language: c++

Adapter Is Doing Real Measurements
..................................

Make sure that the adapter is really doing *measurement* (i.e. *use*
the adaptee) when being asked for its temperature.

.. literalinclude:: /trainings/material/soup/cxx/cxx-code/design-patterns-adapter/tests/adapter-suite-adapter-definitely-knows--a-sensor--HELL.cpp
   :caption: :download:`/trainings/material/soup/cxx/cxx-code/design-patterns-adapter/tests/adapter-suite-adapter-definitely-knows--a-sensor--HELL.cpp`
   :language: c++


.. rubric:: Footnotes
.. [#impedance_mismatch] They sure don't share our ``Sensor``
                         interface. That interface is only internal to
                         our company.