inheritance

问题 So it turns out that I am the last person to discover the fundamental floor that exists in Microsoft's Entity Framework when implementing TPT (Table Per Type) inheritance. Having built a prototype with 3 sub classes, the base table/class consisting of 20+ columns and the child tables consisting of ~10 columns, everything worked beautifully and I continued to work on the rest of the application having proved the concept. Now the time has come to add the other 20 sub types and OMG, I've just

问题 According to cppreference.com, std::shared_ptr provides a full set of relative operators (==, !=, <, ...), but the semantics of comparison aren't specified. I assume they compare the underlying raw pointers to the referenced objects, and that std::weak_ptr and std::unique_ptr do the same. For some purposes, I would prefer to have relative operators that order the smart pointers based on comparing the referenced objects (rather than the pointers to them). This is already something I do a lot,

问题 Virtual Inheritance Memory Layouts I am trying to fully understand what is happening under the hood in the memory with virtual inheritance and vTables/vPtrs and what not. I have two examples of code I have written and I understand exactly why they work however I just want to make sure I have the right idea in my mind, of the object memory layouts. Here are the two examples in a picture, and I just wish to know if my idea of the memory layouts involved are correct. Example 1: class Top {

问题 My question relates to Java, but it also can be applied to C#. I was wondering why everybody recommends making the instance variables private as opposed to making them protected . Let's just think about it. Private variables are not seen by the subclass, so if I need to access or change the variables of the superclass in my subclass I am forced to use some accessor and mutators method like getMyPrivateVariable or setMyPrivateVariable . But when you extend some class and inherit its members,

问题 I have this piece of code (contrived from my real-life trouble) It cannot compile, complaining ExtendsB does not implement B::Run(A* a) . However, it has no problems understanding the extension to A* Run(); class A { }; class ExtendsA : public A { }; class B { public: virtual ~B(){} virtual void Run(A* a) = 0; virtual A* Run() = 0; }; class ExtendsB : public B { public: virtual ~ExtendsB(){} // Not OK! It does not see it as an implementation of // virtual void Run(A* a) = 0; virtual void Run

问题 Everyone seems to generally agree that prototype inheritance is simpler and more flexible than class inheritance. What I have not seen in the literature that I've read is very many examples of things that you can do with prototype inheritance that you cannot with classical. So I pose a simple question: What are some patterns that you can use with prototype inheritance that you cannot with class inheritance and what is the guidance you would give as far when/if to use it? 回答1: One difference

问题 Given the following classes: public abstract class Super { protected static Object staticVar; protected static void staticMethod() { System.out.println( staticVar ); } } public class Sub extends Super { static { staticVar = new Object(); } // Declaring a method with the same signature here, // thus hiding Super.staticMethod(), avoids staticVar being null /* public static void staticMethod() { Super.staticMethod(); } */ } public class UserClass { public static void main( String[] args ) { new

问题 I recently watched Douglas Crockford's JavaScript presentations, where he raves about JavaScript prototype inheritance as if it is the best thing since sliced white bread. Considering Crockford's reputation, it may very well be. Can someone please tell me what is the downside of JavaScript prototype inheritance? (compared to class inheritance in C# or Java, for example) 回答1: Things I miss when sub-classing an existing object in Javascript vs. inheriting from a class in C++: No standard (built

问题 Am I using a feature of Java 8 or misusing it? Refer the code and explanation below to know as to why it was chosen to be like this. public interface Drawable { public void compileProgram(); public Program getProgram(); default public boolean isTessellated() { return false; } default public boolean isInstanced() { return false; } default public int getInstancesCount() { return 0; } public int getDataSize(); public FloatBuffer putData(final FloatBuffer dataBuffer); public int getDataMode();

问题 I changed the highlight color of various of the controls, and I am planning to make more changes. So I though is better to create my own controls and reuse them instead of making the changed for each and every one of them. I created a new user control, and inherited from System.Windows.Forms.ComboBox . The problem is I cannot find a way to override onDraw like I would for onClick . So how I would go and override it? Here is the code I used for each control onDraw event public void