polymorphism

问题 I have a decent understanding about polymorphism but my question is for example, in the code I posted below, what is so special about being able to make an object of Cat while using an animal type for the variable. What purpose does that serve? Also assume that the makenoise method is being override in each objects own class and that the class all the other classes are inheriting from is the animal class. public class Demo { public static void main(String[] args) { Animal a1 = new Cat(); /

问题 What is the better way to reuse implementation: inheritance or generics? The model is following: Script has Steps, Steps have Elements. Tree structure is double linked, i.e. Steps know their Script and Elements now their Step. Now, there are 2 types of Scripts: Templates and Runs, where a Run is created at first as a copy of the Template. This results in 2 similar hierarchies ScriptTemplate->ScriptTemplateStep->ScriptTemplateElement and ScriptRun->ScriptRunStep->ScriptRunElement. Most of the

问题 This question is piggy backing off of the other question I had posted as I'm looking for clarity on how the serialization / validation works with regards to the JsonSubTypes Other question: InvalidSchemaException using JsonSubTypes, not picking up what I defined in the base interface Let's say I have a base class A A implements BaseInterface If I have a sub class B that extends A , but implements it's own interfaces such as AlpahInterface, BetaInterface, CharlieInterface . Herein lies the

问题 This question is piggy backing off of the other question I had posted as I'm looking for clarity on how the serialization / validation works with regards to the JsonSubTypes Other question: InvalidSchemaException using JsonSubTypes, not picking up what I defined in the base interface Let's say I have a base class A A implements BaseInterface If I have a sub class B that extends A , but implements it's own interfaces such as AlpahInterface, BetaInterface, CharlieInterface . Herein lies the

问题 When I tried to understand how to work with collections in java, I realised that I don't understand how polymorphism works for inner classes. Simple code example: class Parent { public static void main(String[] args) { new Parent().newInnerClass().myMethod(); new Child().newInnerClass().myMethod(); } public I newInnerClass() { return new InnerClass(); } private final class InnerClass implements I { @Override public void myMethod() { System.out.println("parent inner class"); foo(); } } public

问题 I saw a few questions about avoiding RTTI, but mine seems to be a bit more specific. Here is an example case: struct Base {}; struct A : Base {}; struct B : Base {}; struct C : Base {}; std::vector<Base*> vec; I want to do something on all possible (unordered) pairs of objects in the vector (if the vector has 3 elements, with 0 and 1, 0 and 2, 1 and 2). The pseudo-code for what I want is something like: if e1 is A and e2 is A: behavior1(e1, e2) elif e1 is A and e2 is B: behavior2(e1, e2) elif

问题 For example, how do I store a list of DataContainers that all use types that derive from the same base class. public class Animal {} public class Cat : Animal {} public class Dog : Animal {} public class DataContainer <TData> where TData : Animal { TData innerObject = new TData (); public TData GetData () { return innerObject; } } public class DataManager { static void Main () { DataContainer<Cat> CatData = new DataContainer<Cat> (); DataContainer<Dog> DogData = new DataContainer<Dog> (); var

问题 Rails 4 ships with strong_parameters, which is a great addition - but I've run into a problem with it. I have a polymorphic model Comment and I cannot for the life of me get the controller to accept the parameters it needs. Here is my code (shortened for clarity): Routes: resources :articles do resources :comments end Models: class Article < ActiveRecord::Base has_many :comments, :as => :commentable end class Comment < ActiveRecord::Base belongs_to :commentable, :polymorphic => true end

问题 I am trying to write a simple custom button in wx.Python. My code is as follows, an error is thrown on line 19 of my "Custom_Button.py" - What is going on? I can find no help online for this error and have a suspicion that it has to do with the Polymorphism. (As a side note: I am relatively new to python having come from C++ and C# any help on syntax and function of the code would be great! - knowing that, it could be a simple error. thanks!) Error def __init__(self, parent, id=-1, NORM_BMP,

问题 I've been banging my head against a wall for sometime on this one. I'm trying to create a class for storing data on People with another class to store their Bank Transactions. Ideally, this all be hidden away and leave only simple statments, declarations and functions available to the programmer. These will include: Dim Clients As New ClientList Clients.Count 'readonly integer Clients.Add("S") Clients.Refresh() Clients(n).Remove() Clients(n).Transaction.Add() Clients(n).Transaction(n).Remove(