Athena Developer Guide

Athena
Chapter 14 Tools and ToolSvc Version/Issue: 2.0.0
14.3 The ToolSvc
The ToolSvc manages Tools. It is its responsibility to create tools and make them available to
Algorithms or Services.
The ToolSvc verifies if a tool type is available and creates the necessary instance after having verified
if it doesn’t already exist. If a tool instance exists the ToolSvc will not create a new identical one but
pass to the algorithm the existing instance. Tools are created on a “first request” basis: the first
Algorithm requesting a tool will prompt its creation. The relationship between an algorithm, the
ToolSvc and Tools is shown in Figure 14.1.
IToolSvc
ToolSvc
IService
IAlgTool
IProperty
ConcreteAlgorithm
AlgTool
IToolFactory
ToolFactory
< T >
ConcreteTool
Figure 14.1 ToolSvc design diagram
The ToolSvc will “hold” a tool until it is no longer used by any component or until the finalize()
method of the tool service is called. Algorithms can inform the ToolSvc they are not going to use a
tool previously requested via the releaseTool method of the IToolSvc interface 1 .
The ToolSvc is created by default by the ApplicationMgr and algorithms wishing to use the
service can retrieve it using the service accessor method of the Algorithm base class as shown in
the lines below.
include "GaudiKernel/IToolSvc.h"
...
IToolSvc* toolSvc=0;
StatusCode sc = service( "ToolSvc",toolSvc);
if ( sc.isFailure) {
...
1. The releaseTool method is not available in this release
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