.. include:: <mmlalias.txt>


Proxy
=====

.. contents::
   :local:

Problem
-------

Say an object lives outside of a client's address space, and a network
protocol must be used to access it from the client's address
space. The object's type has a base type, and it's that base type that
should also be used locally.

The *Proxy* pattern can also be used purely local, for example to hook
into the call to the target object.

Solution: *Proxy*
-----------------

Local Variant
.............

.. .. plantuml::
.. 
..    @startuml
.. 
..    interface Sensor {
..      + get_temperature()
..    }
..    class RandomSensor {
..      + get_temperature()
..    }
..    class ConstantSensor {
..      + get_temperature()
..    }
..    class ProxySensor {
..      + get_temperature()
..    }
.. 
..    ProxySensor -l-> Sensor
.. 
..    Sensor <|.d. RandomSensor
..    Sensor <|.d. ConstantSensor
..    Sensor <|.d. ProxySensor
.. 
..    @enduml

.. image:: /trainings/material/soup/cxx/cxx-exercises/design-patterns/proxy-local.png
   :scale: 40%

Remote Variant
..............

.. image:: /trainings/material/soup/cxx/cxx-exercises/design-patterns/proxy-remote.png

Exercises
---------

* :doc:`/trainings/material/soup/cxx/cxx-exercises/design-patterns/proxy-remote`
* :doc:`/trainings/material/soup/cxx/cxx-exercises/design-patterns/proxy-round`