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ICE C++ question

mcrystalmcrystal Member Mayer CrystalOrganization: Goldman SachsProject: N/A
Please forgive my C++ ignorance, but I am really a Java programmer attempting to write a C++ test and am hoping that someone can point me in the right direction. I have a slice file which essentially defines a bunch of interfaces and classes. The basic structure is I have a base class which is extended by a bunch of subclasses and I have a base service interface which is extended by subinterfaces:

ClassA
ClassB : ClassA

ServiceX {
virtual ClassA getA();
}

ServiceY : ServiceX {
getA() {
return ClassB();
}
}

In C++ the interface generates something like:
ClassAPtr getA();

where ClassAPtr is the rerference counted pointer (IceInternal::Handle) which is typedefed in the generated header file. My question is, how does one properly downcast this to the actual implementation class. In Java one would do something like:

ClassB val = (ClassB)ServiceY.getA();

How do I accomplish this same functionality in C++?


Thanks again,
Mayer

Comments

  • mesmes CaliforniaAdministrators, ZeroC Staff Mark SpruiellOrganization: ZeroC, Inc.Project: Ice Developer ZeroC Staff
    Hi,

    In C++, we usually recommend that you create a smart pointer type for implementation classes. For example:
    // C++
    class ClassAI : public ClassA { ... };
    typedef IceUtil::Handle<ClassAI> ClassAIPtr;
    
    Having done that, you can downcast quite easily:
    ClassAPtr a = ...
    ClassAIPtr ai = ClassAIPtr::dynamicCast(a);
    if(ai) {
        // dynamicCast may return nil!
    }
    
    In the absence of a typedef for your implementation class, you can use the normal C++ mechanism:
    ClassAPtr a = ...
    ClassAI* ai = dynamic_cast<ClassAI*>(a.get());
    if(ai) {
        ...
    }
    
    Hope that helps,
    - Mark
  • mesmes CaliforniaAdministrators, ZeroC Staff Mark SpruiellOrganization: ZeroC, Inc.Project: Ice Developer ZeroC Staff
    After re-reading your post, it sounds like you simply want to downcast to another Slice-defined type. In this case you would use the same technique I described above:
    ClassAPtr a = ...
    ClassBPtr b = ClassBPtr::dynamicCast(a);
    if(b) {
        ...
    }
    
    - Mark
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