4.0 Interfaces

Initially, in v1.0 of CrxOop, CrxOop did not allow the creation of pure virtual methods, while at the same time the Javscript technology does not allow a satisfactory implementation of multiple inheritance for classes. This leads to the implementation of what are called interfaces in Java. In C++, these would be classes with only public pure virtual methods.

Note the following:

• Interfaces do not define variables
• Interfaces do not define full function signatures due to Javascript's limitations, only function names
• Interface supports multiple inheritance to other interfaces
• Interface can not be instantiated
• A class may implement multiple interfaces
• A class implements an interface by defining a public virtual function, or a public pure virtual function with the same name as the name declared in the interface definition, and doing this for all functions declared in the interface definition.
• Although virtual functions may have different accessors set going down the class extension chain, once a virtual function is required by an interface, pertaining classes in the class extension chain may only define said virtual function as public.
• Class instances can not be cast to interfaces
• Interfaces are still a type, and class instances can be checked against them