ApplicationSingletonApplicationSingleton — allows creation of only one instance of the class.
ApplicationSingleton (klass)
klassThe name of a class.
The instance of the class named by klass.
This function creates a singleton based on the name of a class, which in most
cases is desirable. This is useful because a class is routinely redefined by
reloading its corresponding file, The alternative, ApplicationMultiple gives instances of
the class the same name but not the same definition.