multiple-inheritance | 易学教程

Are multiple-inherited constructors called multiple times?

阅读更多关于 Are multiple-inherited constructors called multiple times?

问题 Are multiple-inherited constructors called multiple times? And in what order are constructors called? Does this depend on the order in the inheritance list? Here is an example (it's only for making the situation clear, no real-life example). class Base {}; class DerivedBaseOne : public Base {}; class DerivedBaseTwo : public Base {}; class Derived : public DerivedBaseTwo, public DerivedBaseOne {}; //somewhere in the code, is Base() called two times here? Derived * foo = new Derived(); Is the

Multiple Inheritance in Java since All classes extend from Object class? [duplicate]

阅读更多关于 Multiple Inheritance in Java since All classes extend from Object class? [duplicate]

问题 This question already has an answer here: Java : If A extends B and B extends Object, is that multiple inheritance 11 answers I have a simple question: If I declare a class A - means this class in implicitly inheriting from Object Class. Now If class B inherits from class A is this Class B also not Inheriting from Object class ? If yes, does that mean writing the keyword 'extends' some how override the implicit inheritance ( from class Object) ? 回答1: All classes extend form Object , either

C++ multiple inheritance order

阅读更多关于 C++ multiple inheritance order

问题 I'm trying to understand the affect of inheritance order in C++.. I looked online, but I couldn't find a clear and sufficient answer... So, for the sake of the question, assume there are 2 classes: class B and class C. Now, define: class A1 : public B, public C{ ... }; class A2 : public C, public B{ ... }; What is the difference between A1 and A2? Thanks a lot! 回答1: The order of derivation is relevant only to determine the order of default initialization by constructors and cleanup by

How to implement multiple inheritance in delphi?

阅读更多关于 How to implement multiple inheritance in delphi?

I'm doing a full rewrite of an old library, and I'm not sure how to handle this situation (for the sake of being understood, all hail the bike analogy): I have the following classes: TBike - the bike itself TBikeWheel - one of the bike's wheel TBikeWheelFront and TBikeWheelBack , both inherits from TBikeWheel and then implements the specific stuff they need on top of it This is pretty straightforward, but now I decide to create multiple kind of bikes, each bikes having it's own kinds of wheel - they do the same stuff as a regular front/back wheels, plus the specific for that bike. TBikeXYZ -

Custom Exceptions in C++

阅读更多关于 Custom Exceptions in C++

问题 I've been trying to make some custom exception classes for a C++ library I'm working on. These custom exceptions capture extra info, such as file,line number,etc, needed for debugging, if for some reason while testing an exception is not caught in the right place. However most people seem to recommend inheriting from the std::exception class in the STL, which I agree with, but I was wondering maybe it would be better to use multiple inheritance to inherit from each of the derived std:

C++ - downcasting a diamond shape inherited object without RTTI/dynamic_cast

阅读更多关于 C++ - downcasting a diamond shape inherited object without RTTI/dynamic_cast

问题 I'm currently working on integrating a third-party package that uses lots of RTTI stuff on a non-RTTI platform (Android). Basically, I did my own RTTI implementation but I'm stuck on a problem. The issue is that a lot of classes are having the diamond inheritance problem since all the classes derive from the same base class (object).. and so, if I want to downcast from the base class to the derived class, I have to use a dynamic_cast - but RTTI is not available! How do I convert an object

Multiple inheritance + virtual function mess

阅读更多关于 Multiple inheritance + virtual function mess

I have a diamond multiple inheritance scenario like this: A / \ B C \ / D The common parent, A, defines a virtual function fn(). Is it possible for both B and C to define fn() ? If it is, then the next question is - can D access both B and C's fn() without disambiguation? I'm assuming there is some syntax for this.. And is it possible for D to do that without knowing specifically who are B and C? B and C can be replaces by some other classes and I want the code in D to be generic. What I'm trying to do is to have D somehow enumerate all of the instances of fn() it has in its ancestry. Is this

Are Mixin class init functions not automatically called?

阅读更多关于 Are Mixin class __init__ functions not automatically called?

I'd like to use a Mixin to always add some init functionality to my child classes which each inherit from different API base classes. Specifically, I'd like to make multiple different child classes that inherit from one of these different API-supplied base classes and the one Mixin, which will always have the Mixin initialization code executed in the same way, without code replication. However, it seems that the __init__ function of the Mixin class never gets called unless I explicitly call it in the Child class's __init__ function, which is less than ideal. I've built up a simple test case:

Is Multiple Inheritance allowed at class level in PHP?

阅读更多关于 Is Multiple Inheritance allowed at class level in PHP?

Is Multiple Inheritance allowed at class level in PHP? 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 ? You are encouraged to either use object composition or interfaces (which do allow multiple inheritance) or - if you are after horizontal reuse - look into the Decorator or Strategy pattern until we have Traits (or Grafts or whatever they

Can one class extend two classes?

阅读更多关于 Can one class extend two classes?

My class should extend two classes at the same time: public class Preferences extends AbstractBillingActivity { public class Preferences extends PreferenceActivity { How to do so? Upd . Since this is not possible, how should I use that AbstractBillingActivity with Preferences then? Upd2 . If I go with interfaces, should I create: BillingInterface public interface BillingInterface extends PreferenceActivity, AbstractBillingActivity { } PreferenceActivity public interface PreferenceActivity { } AbstractBillingActivity public interface AbstractBillingActivity { void onCreate(Bundle