The IDL (Interface Definition Language) file is the component's definition. It contains the functions the component exposes and the interface it must implement, regardless of the language in which is implemented.

In this link you can find details about IDL syntax and definitions.

Set IDL for our hello-world components

For any given component we have to follow 3 steps:

1. Implement component's IDL
2. Implement component
3. Install component in ACS

So, we create the component's IDL directory and file

In this tutorial we will write and run example ACS modules in Python, Java and C++.. First we must  perform some configurations on ACS before coding our components.

Set $INTROOT environment variable

Visit ACS Directory Structure#INTROOT for full details. This directory is where our experimental components will be installed.

export INTROOT=~/workspace/introot
getTemplateForDirectory INTROOT $INTROOT

Pro tip: you can set $INTROOT in your ~/.bashrc to avoid setting $INTROOT manually in every new terminal.

echo INTROOT=~/workspace/introot >> ~/.bashrc

Set IDL

First we create the directory for the IDL:

cd ~/workspace
getTemplateForDirectory MODROOT_WS idlHelloComp
cd idlHelloComp/src
touch ../idl/HelloComponent.idl
sudo nanovim ../idl/HelloComponent.idl

...

#ifndef _HELLOCOMPONENT_IDL_
#define _HELLOCOMPONENT_IDL_

#pragma prefix "acsws"

#include <acscomponent.idl>

module workshop {
    interface HelloComponent : ACS::ACSComponent {
        string printHello();
    };
};

#endif

We modify add our component's IDL to the Makefile:

vim ~/workspace/idlHelloComp/src/Makefile

...
IDL_FILES = HelloComponent
HelloComponentStubs_LIBS = acscomponentStubs
...
COMPONENT_HELPERS=on
...

...

make -j all install