Revision as of 15:35, 13 May 2006

The UNO C++ Language

The aim of this chapter is to explain peculiarities of the C++ language in the UNO environment and not to provide skills on traditional C++. To put it differently, I want to give here the UNO/C++ background, quite helpful in getting us started. You can find e-Books on C++ here.

Our starting Example : Simple Binaries (Executable)

We want now to start with a SDK example. The purpose of the example presented is to create an executable which interacts with OpenOffice.org. We can imagine two kind of interactions : direct interaction with OpenOffice.org or interaction with one of OOo's shared library. We focus on this second case where the makefile is simpler. The shared library involved is then cppuhelper.uno.so (cppuhelper.uno.dll under Windows). Former case will be examined later. I assume (I know nobody of the SDK team) this example is given to provide the simplest example we can do with the SDK. This is the Lifetime example : see at “<OpenOffice.org1.1_SDK>/examples/DevelopersGuide/ProfUNO/Lifetime”

Before diving into the examples, you will need to set up your programming environment so you can create UNO programs. What's required depends on what platform you're working. This is shown in the first example with LINUX platform. To check this example you only have to launch the makefile :

cd <OpenOffice.org1.1_SDK>
./setsdkenv_unix
cd examples/DevelopersGuide/ProfUNO/Lifetime
make
make ProfUnoLifetime.runexe

The last command line only launch the binary executable “ProfUnoLifetime” which interact with cpphelper.uno.so (cppuhelper.uno.dll under Windows) even if OpenOffice.org is not running. This example only create and release an object, not more. The constructor and destructor of the object only write out a message. Its little size allow us to give its code here :

// C++
#include <stdio.h>
#include <cppuhelper/weak.hxx>

class MyOWeakObject : public ::cppu::OWeakObject
{
public:
    MyOWeakObject() { fprintf( stdout, "constructed\n" ); }
    ~MyOWeakObject() { fprintf( stdout, "destructed\n" ); }
};


void simple_object_creation_and_destruction()
{
    // create the UNO object
    com::sun::star::uno::XInterface * p = new MyOWeakObject();

    // acquire it, refcount becomes one
    p->acquire();

    fprintf( stdout, "before release\n" );

    // release it, refcount drops to zero
    p->release();

    fprintf( stdout, "after release\n" );
}


int main( char * argv[] )
{
    simple_object_creation_and_destruction();
    return 0;
}

The two methods acquire and release will be encounter later. What they exactly do is not important for the moment. This example recall us how to write a class which inherits from an other class, how to write and call methods and how to instantiate the class. All the listings given below only need to modify this C++ code compile it and run it. You can therefore use the same makefile by possibly changing the name of the source file (tackled in next section).

Types

The UNO types are given in the table below :

Table de vérité