inheritance

问题 Suppose I am writing some classes to perform simple mathematical operations, and that I have an abstract class JNumber with a method in it for adding on another number: public abstract class JNumber { public abstract JNumber add(JNumber addend); // etc. } The return value from add represents the sum of this with the parameter addend . Now suppose that I have an abstract subclass (called JFieldElement ) of JNumber which includes a method for division (I cannot have this method in the JNumber

问题 I can use this syntax for inheriting a class in SASS Code .message { border: 1px solid #ccc; padding: 10px; color: #333; } .success { @extend .message; border-color: green; } Output .message, .success, .error, .warning { border: 1px solid #cccccc; padding: 10px; color: #333; } .success { border-color: green; } I want to do something similar, whereby .message is omitted from the output Desired Output .success, .error, .warning { border: 1px solid #cccccc; padding: 10px; color: #333; } .success

问题 I am having issues finding good documentation for the problem I am having. I am reconstructing a portion of an enterprise solution and swapping over the NHibernate for our ORM. I have 3 tables which I want to all inherit from each other. MasterAccount : Account : InvBilling **MasterAccount** id_MasterAccount **Account** id_Account id_MasterAccount id_InvBilling **InvBilling** id_InvBilling id_MasterAccount For each row in MasterAccount there exists a row in Account where the Id_MasterAccount

问题 I am working with postgreSOL. I have a parent table and child table, which inherits the parent table.I create a trigger for the parent table. Is this trigger is propagated to child table? Any possible techniques to inherit the trigger also is available? 回答1: No, it isn't. You should write another trigger for the child table. Based on what your trigger should do, in same situations you can use the trigger on the parent table. For example, that trigger could decide in which table the data

问题 Duplicate of C# Accessing a subclass property - see additional solution approaches there. I have an object model where each object has a parent and I would like to access the parent property with the specific type for each object. So e.g. Wheel shall have a parent property of type Car. My guess is that there is an established design pattern for achieving this (in .NET). However, I have not found it so the design I came up with looks like this public class BaseObject<T> where T : BaseObject<T>

问题 I was looking at this video explanation(https://www.youtube.com/watch?v=qMO-LTOrJaE) of JS prototypal inheritance. There's something I don't understand. Let me explain var Bear = function(type) { //PARENT this.type; this.hasFur = true; } Bear.prototype.kingdom = 'Animalia'; //ASSIGNING TO PARENT'S PROTOTYPE var Grizzly = function(type) { //CHILD this.species = 'Brown Bear'; } Grizzly.prototype = Object.create(Bear.prototype); //INHERITING FROM PARENT var grizzly1 = new Grizzly('grizzly');

问题 I have a around 50 databases that have 150 tables each and working on a search mechanism that would allow to query the tables that have specific columns. Most database structures are similar so idea was to generate EF entities and put interfaces behind the entities generated if tables that they are being generated from have specific columns, so that I could later query then on that column. After doing this I ran into unexpected problem on some tables column I am trying to map is Long while on

问题 Assume class Animal which does Eat, Sleep and Make Noise. Assume class Mammal : public Animal which also does MakesBaby Assume that Mammal also does Eat, Sleep and Make Noise which it inherits from Animal. This code is extended from code presented in this question which was answered yesterday by Dan Masek. The problems with this code are: Mammal can't inherit from Animal (compile error) Mammal cannot Eat, Sleep or Make Noise Code suffers from "Needless Repetition", thus meeting with the scorn

问题 It's, I think somethin basic in OOP : Environment : C#/.net 2.0 Let's say I have two class : public class Animal { } public class Dog : Animal { } A service class with two method : public void DoStuff(Animal animal) { Console.Write("Animal stuff"); } public void DoStuff(Dog animal) { Console.Write("Dog stuff"); } If I execute the following code : Animal instance = new Animal(); MyService.DoStuff(instance); Animal instance2 = new Dog(); MyService.DoStuff(instance2); "Animal stuff" is printed

问题 I have a class, let's call it Polynomials. The number of needed Polynomials are not known in advance and are determined at run-time. My current implementation uses a container class, let's call it Solutions, in which there is a vector, let's call it polynomialVector, it is defined this way: std::vector<Polynomial> polynomialVector; The vector is created and populated in this way (The constructor of Solutions do this job): polynomialVector.reserve(numberofneededpolynomials); for(int i = 0; i <