If you have an interface hierarchy and a corresponding implementation hierarchy, making the interface base classes virtual bases is necessary. E.g. struct IBasicInterface { virtual ~IBasicInterface() {} virtual void f() = 0; }; struct IExtendedInterface : virtual IBasicInterface { virtual ~IExtendedInterface() {} virtual void g() = 0; }; // One possible implementation strategy struct CBasicImpl … Read more
Ok i found out a pretty decent solution: basically i need to unpack one extra lambda case and apply the using clause to the unpacked lambda and the rest, but in this case, since i apparently i cannot make a variadic list of using declarations (at least i don’t know the syntax, if its possible), … Read more
While the type parameters of a generic method can be restricted by bounds, such as extends Foo & Bar, they are ultimately decided by the caller. When you call getFooBar(), the call site already knows what T is being resolved to. Often, these type parameters will be inferred by the compiler, which is why you … Read more
It was a design decision of Java. You’ll never get it, so don’t worry too much about it. Although MI might help you make Mixins, that’s the only good MI will ever do you.
Even if B is indeed derived from Clonable<B>, the problem here is that Clonable<B> construction is not valid, as it defines B* clone() const override which of course is not an override of AbstractClonable::clone(), since the compiler doesn’t see B at this point as a child of AbstractClonable. So I believe the issue lays in … Read more
Unfortunately, this does not quite do what you want. A using directive is just about bringing some names into the scope it is used. virtual methods need be overriden, and just bringing names is not considered overriding. The truth of the matter is that C++ does not support delegation directly. There is just this slight … Read more
Multiple inheritance suffers from the Diamond Problem, which has not been (agreed upon how to be) solved in PHP yet. Thus, there is no multiple inheritance in PHP. BaseClass /\ / \ ClassA ClassB \ / \/ ClassC If both ClassA and ClassB defined their own method foo(), which one would you call in ClassC? … Read more
For all practical purposes, there is no limit on the number of interfaces a class can implement, but java does not let you inherit from multiple superclasses. However, if you really want to nitpick, you can say that the number of interfaces a class can implement is bound by the maximum value the interface id … Read more
super is indeed intended for this situation, but it only works if you use it consistently. If the base classes don’t also all use super it won’t work, and unless the method is in object you have to use something like a common base class to terminate the chain of super calls. class FooBase(object): def … Read more
Java does not support multiple inheritance. There are a few workarounds I can think of: The first is aggregation: make a class that takes those two activities as fields. The second is to use interfaces. The third is to rethink your design: does it make sense for a Preferences class to be both a PreferenceActivity … Read more