Difference between revisions of "Documentation/DevGuide/ProUNO/C++/Mapping of Singletons"

Revision as of 15:07, 8 May 2008

A new-style singleton of the form

 singleton Name: XIfc;

is mapped to a C++ class with the same name. The class has a single member function

 public:
 static com::sun::star::uno::Reference< XIfc > get(
     com::sun::star::uno::Reference< com::sun::star::uno::XComponentContext > const & context) 
     throw (com::sun::star::uno::RuntimeException) { ... }

The semantics of such a singleton getter function in C++ are as follows (they are the same as for Java):

• The com.sun.star.uno.XComponentContext argument must be non-null.
• The singleton getter uses com.sun.star.uno.XComponentContext:getValueByName to obtain the singleton instance (within the "/singletons/" name space).
• If no singleton instance could be obtained, the singleton getter fails by throwing a com.sun.star.uno.DeploymentException. The net effect is that a singleton getter either returns the requested non-null singleton instance, or throws an exception; a singleton getter will never return a null instance.

Old-style services are not mapped into the C++ language binding.