Basic Steps for Implementing SOM Classes

Implementing and using SOM classes in C or C++ involves the following steps, which are explicitly illustrated in the examples of this tutorial:

• Define the interface to objects of the new class (that is, the interface declaration), by creating a .idl file.

• Run the SOM Compiler on the .idl file (by issuing the sc command on AIX or OS/2, or by issuing the somc command on Windows) to produce the following binding files:

  • Template implementation file
    a .c file for C programmers, or
    a .C file (on AIX) or a .cpp file (on OS/2 or Windows) for C++ programmers;

  • Header file to be included in the implementation file
    a .ih file for C programmers, or
    a .xih file for C++ programmers; and

  • Header file to be included in client programs that use the class
    a .h file for C clients, or
    a .xh file for C++ clients.
  To specify whether the SOM Compiler should produce C or C++ bindings, set the value of the SMEMIT environment variable or use the "-s" option of the sc or somc command, as described in Section 4.3, "The SOM Compiler." By default, the SOM Compiler produces C bindings.

Customize the implementation, by adding code to the template implementation file.

Create a client program that uses the class.

Compile and link the client code with the class implementation, using a C or C++ compiler.

Execute the client program.

The following examples illustrate appropriate syntax for defining interface declarations in a .idl file, including designating the methods that the class's instances will perform. In addition, example template implementation files contain typical code that the SOM Compiler produces. Explanations accompanying each example discuss topics that are significant to the particular example; full explanations of the SOM IDL syntax are contained in Chapter 4, "SOM IDL and the SOM Compiler." Customization of each implementation file (step 3) is illustrated in C and C++.

Note:

• The Tutorial assumes you will work through the examples in order. If you do not do so, the code that the SOM Compiler generates from your revised .idl file may vary slightly from what you see in the Tutorial.

• When the SOMobjects Toolkit is installed, a choice is made between "somcorba" and "somstars" for the style of C bindings the SOM Compiler will generate. The Tutorial examples use the "somcorba" style, where an interface name used as a type indicates a pointer to an object, as required by strict CORBA bindings. Consequently, as the examples show, a "*" does not explicitly appear for types that are pointers to objects. If your system was installed for "somstars" C bindings, you can set the environment variable SMADDSTAR=1 or use the SOM Compiler option "-maddstar" to request bindings that use explicit pointer stars. For more information, see "Declaring object variables" in Chapter 3, "Using SOM Classes in Client Programs" and "Object types" in Chapter 4, "SOM IDL and the SOM Compiler."