inheritance

问题 I am having trouble understanding how inheritance works in Java when inner classes are present. I'm currently working on something where a child class needs to slightly change the functionality of the inner class of it's parent. I've come up with an simpler, analagous example below. I expected this code to print "I am a ChildClass.InnerClass" but instead it prints "I am a ParentClass.InnerClass". Why is this? Also, if I change the obj object in main to be of type ChildClass then the output

问题 This question already has answers here : templates: parent class member variables not visible in inherited class (3 answers) Closed 4 years ago . The following code cannot compile - use of undeclared identifier. I use GCC and XCode for compilation. Everything is in a single header file. include "MyArray.h" template <typename T> class MyBase { public: MyBase(); virtual ~MyBase(); void addStuff(T* someStuff); protected: MyArray<T*> stuff; }; template <typename T> MyBase<T>::MyBase() {} template

问题 Why is @ForceDiscriminator or its equivalent @DiscriminatorOptions(force=true) necessary in some cases of inheritance and polymorphic associations? It seems to be the only way to get the job done. Are there any reasons not to use it? 回答1: As I'm running over this again and again, I think it might help to clarify: First, it is true that Hibernate does not require discrimination when using JOINED_TABLE mapping. However, it does require it when using SINGLE_TABLE . Even more importantly, other

问题 Im wondering which way of using OOP in Javascript ist best way to go with. There is this prototype thing and you have the function style way. But both have very bad ways to inherit a base class. So I tried to build a way to make this possible without having to use prototype and such. function Car(name) { this.Name = name; this.FullName = function () { return this.Name; } } function SpecialCar(name, variant) { //BaseClass.apply(this, PARAMS AS ARRAY); Car.apply( this, [name] ); //new property

问题 i am pretty new to the repository design pattern and i have reached a dead end while trying to implement it, with regards to inheritance. I am not sure even if i started in the right direction. So basically i will have an abstract base class Product, with id and imagePath for instance, and will have several products which inherit from this. namespace Common { public abstract class Product { public int Id { get; set; } public string ImgPath { get; set; } } public class Scale : Product { public

问题 Let's say I have some base class: class Task: def run(self): #override this! Now, I want others to subclass Task and override the run() method: class MyTask(Task): def run(self): #successful override! However, the problem is that there is logic that must take place before and after the run() method of every class that subclasses Task. It seems like one way I could do this would be to define another method in the base class which then calls the run() method. However, I wanted to ask, is there

问题 This is an extension of this questionand probably might even be a duplicate of some other question(If so, please forgive me). I see from MSDN that generics are usually used with collections The most common use for generic classes is with collections like linked lists, hash tables, stacks, queues, trees and so on where operations such as adding and removing items from the collection are performed in much the same way regardless of the type of data being stored. The examples I have seen also

问题 I have a servlet that, passed on query params, gets a list of objects from the DAO, turns the list into JSON, and sends it back in the response. Every list is made of objects that have a method: public String getAsJson(){...} And the servlet has a bunch of mostly indentical methods that look like: private String getUserListAsJson() { List<User> userList = this.dao.getUsers(); StringBuilder builder = new StringBuilder(); builder.append('['); // loops over the list appending the value of each

问题 I'm doing a heavy bit of reflection in my current project, and I'm trying to provide a few helper methods just to keep everything tidy. I'd like to provide a pair of methods to determine if a type or instance implements IEnumerable – regardless of the type T . Here is what I have at the moment: public static bool IsEnumerable(this Type type) { return (type is IEnumerable); } public static bool IsEnumerable(this object obj) { return (obj as IEnumerable != null); } When I test them using Debug

问题 The topic of how C# virtual and override mechanism works internally has been discussed to death amongst the programmers... but after half an hour on google, I cannot find an answer to the following question (see below): Using a simple code: public class BaseClass { public virtual SayNo() { return "NO!!!"; } } public class SecondClass: BaseClass { public override SayNo() { return "No."; } } public class ThirdClass: SecondClass { public override SayNo() { return "No..."; } } class Program {