= Introduction = 

In this tutorial we will learn how to add a new component to an existing PACPUS project. 
Before starting, please make sure that your installation of PACPUS framework works fine, follow the guide here: GettingStarted

We make the assumption that we works in a Linux environment. 

= Goal = 

So we will add a component to the [source:pacpussensors pacpussensors] project that will generate a string and send it to an ouput. 

= Explanations = 

== step 1: getting the source code of the project and compile it == 

Go to your development folder, typically it may ~/dev/pacpus and get the source code of the SVN repository and compile the project: 

{{{
svn co https://devel.hds.utc.fr/svn/pacpussensors/trunk pacpussensors
}}}

We will keep only the PacpusSocket plugin for this example. Edit the CMakeLists.txt in the pacpussensors directory and comment all {{{add_subdirectory(...)}}} commands except of {{{add_subdirectory(PacpusSocket)}}}. You will get something like this: 

{{{
# ========================================
# Build the PacpusSensors' modules
# ========================================
#
# In the following list add the plugin you want to build. 
# Paths are relative to the root of the project. 
#

#add_subdirectory(Alasca)
#add_subdirectory(CanGateway)       #require kvaser libcan
#add_subdirectory(PtGreyCameras)
#add_subdirectory(Dualshock)
#add_subdirectory(NMEA0183)
#add_subdirectory(Gps)              #require NMEA0183
#add_subdirectory(SpanCPTComponent) #require NMEA0183
#add_subdirectory(Sick)
add_subdirectory(PacpusSocket)
#add_subdirectory(OpencvVideo)
#add_subdirectory(Wifibot)         #depends on PacpusSocket, change PacpusSocket to PacpusUdpSocket 
#add_subdirectory(Ladybug)         #require Ladybug spherical camera's driver, not compiled yet
#add_subdirectory(StdDbtPlayerComponents) 
#add_subdirectory(TelnetClient)
#add_subdirectory(VelodyneComponent)
}}}

To compile the project we will do it with QtCreator (please read the page to knwow how to configure correctly the project regarding pacpus needs). Open the software, then select the menu {{{File->Open File or Project}}} and choose the root {{{CMakeLists.txt}}} (in ~/dev/pacpus/pacpussensors/ if you have followed the guidelines). 

In the Build menu, launch the building process, the results of a correct compilation is: 
{{{
[100%] Built target PacpusSocket
Install the project...
-- Install configuration: ""
-- Installing: /opt/pacpus/0.2.3/bin/libPacpusSocket.so
-- Removed runtime path from "/opt/pacpus/0.2.3/bin/libPacpusSocket.so"
-- Installing: /opt/pacpus/0.2.3/include/PacpusSocket
-- Up-to-date: /opt/pacpus/0.2.3/include/PacpusSocket/PacpusUDPSocket.h
-- Installing: /opt/pacpus/0.2.3/include/PacpusSocket/PacpusSocketConfig.h
-- Installing: /opt/pacpus/0.2.3/include/PacpusSocket/PacpusSocketPlugin.h
-- Up-to-date: /opt/pacpus/0.2.3/include/PacpusSocket/PacpusSocketAirplug.h
}}}

The {{{PacpusSocket.so}}} plugin and headers files should be installed in your PACPUS_ROOT folder. 


== Step 2: writing the {{{StringGenerator}}} component == 

We will add the {{{StringGenerator}}} component to the {{{pacpussensors}}} project. Instead of adding a new plugin, we will include this component to the {{{PacpusSocket}}} plugin. 

So go to the !PacpusSocket folder and create 2 new files: 
- {{{StringGenerator.h}}}: the declaration of the component, the class may inherit from {{{QObject}}} (needed for the input/output mechanism) and {{{ComponentBase}}} (mandatory to be a pacpus component)
- {{{StringGenerator.cpp}}}: the implementation of the component that must follow the component interface, ie: 
  - a declaration of a {{{ComponentFactory}}}: {{{static ComponentFactory <MyClassComponent> sFactory("MyComponentTypeForTheXml");}}}
  - a specific constructor with a QString parameter: {{{MyClassComponent::MyClassComponent(QString name) : ComponentBase(name)}}}
  - the 5 pacpus methods: 
     - {{{void MyClassComponent::startActivity()}}}
     - {{{void MyClassComponent::stopActivity()}}}
     - {{{ComponentBase::COMPONENT_CONFIGURATION  MyClassComponent::configureComponent(XmlComponentConfig config)}}}
     - {{{void MyClassComponent::addInputs()}}}
     - {{{void MyClassComponent::addOutputs()}}}


Add these 2 files to the {{{CMakeLists.txt}}} of the {{{PacpusSocket}}} plugin: 
- put the cpp file to {{{PROJECT_SRCS}}} variable
- put the header file to {{{PROJECT_HDRS}}} and  {{{FILES_TO_MOC}}} variables 
 
Then compile the project again in QtCreator, you may get the same {{{PacpusSocket.so}}} plugin but at the difference it contains a new component. 

You can find the template files for this component in this archive: raw-attachment:StringGeneratorTemplate.tar.gz

== Step 3: coding the string generation algorithm ==

To generate the string at a fixed rate we will use a {{{QTimer}}} object. 


== Step 4: testing ==