Athena Developer Guide

Athena Chapter 18 Framework packages, interfaces and libraries Version/Issue: 2.0.0
18.3 Interfaces in Gaudi
One of the main design choices at the architecture level in Gaudi was to favour abstract interfaces when
building collaborations of various classes. This is the way we best decouple the client of a class from its
real implementation.
An abstract interface in C++ is a class where all the methods are pure virtual. We have defined some
practical guidelines for defining interfaces. An example is shown in Listing 18.1:
Listing 18.1 Example of an abstract interface (IService)
1: // $Header: $
2: #ifndef GAUDIKERNEL_ISERVICE_H
3: #define GAUDIKERNEL_ISERVICE_H
4:
5: // Include files
6: #include "GaudiKernel/IInterface.h"
7: #include
8:
9: // Declaration of the interface ID. (id, major, minor)
10: static const InterfaceID IID_IService(2, 1, 0);
11:
12: /** @class IService IService.h GaudiKernel/IService.h
13:
14: General service interface definition
15:
16: @author Pere Mato
17: */
18: class IService : virtual public IInterface {
19: public:
20: /// Retrieve name of the service
21: virtual const std::string& name() const = 0;
22: /// Retrieve ID of the Service. Not really used.
23: virtual const IID& type() const = 0;
24: /// Initilize Service
25: virtual StatusCode initialize() = 0;
26: /// Finalize Service
27: virtual StatusCode finalize() = 0;
28: /// Retrieve interface ID
29: static const InterfaceID& interfaceID() { return IID_IService; }
30: };
31:
32: #endif // GAUDIKERNEL_ISERVICE_H
33:
From this example we can make the following observations:
page 160
• Interface Naming. The name of the class has to start with capital “I” to denote that it is an
interface.