inheritance

问题 I've been following the tutorial here, except as I'm not creating a code snippet web-tool, I'm creating a RPG character manager, I've been swapping out ' snippet ' with ' mage '. The other major difference is that my Mage only has a hold of users via their superclass NWODCharacter (this is so I can later on add other character types, like Werewolves and Vampires!) On accessing http://localhost:8000/users/ I get this error: AttributeError at /users/ 'User' object has no attribute 'mages'

问题 I'm a bit confused about how Java generics handle inheritance / polymorphism. Assume the following hierarchy - Animal (Parent) Dog - Cat (Children) So suppose I have a method doSomething(List<Animal> animals) . By all the rules of inheritance and polymorphism, I would assume that a List<Dog> is a List<Animal> and a List<Cat> is a List<Animal> - and so either one could be passed to this method. Not so. If I want to achieve this behavior, I have to explicitly tell the method to accept a list of

问题 I have create three classes. One class is db which extends from PDO. Other two class extends from the db class. But the problem is when I initialize objects of these sub classes the second object is created as clone of the first object. Thanks in advance for any help. <?php /** The Database Driver */ define('DB_DRIVER', 'mysql'); /** The name of the database */ define('DB_NAME', 'sample'); /** MySQL database username */ define('DB_USER', 'root'); /** MySQL database password */ define('DB

问题 Here is an example of class Animal and its child class Bird definition in JavaScript (using TypeScript): class Animal { name: string; numberOfLegs: number = 4; aboutMe: string; constructor (theName: string) { this.name = theName; this.init(); } init() { this.aboutMe = `I'm ${this.name} with ${this.numberOfLegs} legs`; } } class Bird extends Animal { numberOfLegs: number = 2; constructor (theName: string) { super(theName); } } var bird = new Bird('Bimbo'); console.log(bird.aboutMe); The

问题 I was fiddling around with inheritance recently and I'm a little confused by the behaviour of the following: class Foo(list): def method(self, thing): new = self + [thing] print(new) self = new print(self) def method2(self, thing): self += [thing] >>> f = Foo([1, 2, 3, 4, 5]) >>> f.method(10) [1, 2, 3, 4, 5, 10] [1, 2, 3, 4, 5, 10] >>> f [1, 2, 3, 4, 5] >>> f.method2(10) >>> f [1, 2, 3, 4, 5, 10] Why does the in-place method method2 work but the first one doesn't? 回答1: Because that's how in

问题 I have a parent class in Java called Flight . I have children classes: JetFlight , NormalFlight , etc. which inherit from Flight . I want all the children classes to implement compareTo from the Comparable interface. I want them to inherit from Flight because I want to use polymorphism (for example, initiate a Flight array and fill it with objects of JetFlight , NormalFlight , etc.). This is my code for the parent class: public abstract class Flight { public abstract int compareTo(Object o);

问题 I have a parent class in Java called Flight . I have children classes: JetFlight , NormalFlight , etc. which inherit from Flight . I want all the children classes to implement compareTo from the Comparable interface. I want them to inherit from Flight because I want to use polymorphism (for example, initiate a Flight array and fill it with objects of JetFlight , NormalFlight , etc.). This is my code for the parent class: public abstract class Flight { public abstract int compareTo(Object o);

问题 I know about protocols and protocol extensions being the best way to emulate abstract classes, but what I want to do needs real abstract classes I think. I want a BaseCollectionViewCell and a BaseCollectionViewSource that work together. You'd pass an array to a subclass of the BaseCollectionViewSource and implement a method that returns a reuse identifier. The cell would be instantiated by the BaseCollectionViewSource and have a method setData that would be overridden in the concrete

问题 I have a bunch of DTO classes that inherit from this CardBase : // base class public class CardBase { public int TransId {get; set; } public string UserId { get; set; } public int Shift { get; set; } } // one of the concrete classes public class SetNewCardSettings : CardBase { // specific properties ... } In my MVC project I have a bunch of view models with a AuditVm complex type that has the same properties of CardBase : public class AuditVm { public int TransId {get; set; } public string

问题 I want my Player objects to inherit the sum of chips in the Tournament. I get (Attempted to divide by zero.) and I think that's because it fails to inherit Chips from the parent Tournament object. Why is this not working? public partial class Form1 : Form { public Tournament Tournament { get; set; } public Form1() { InitializeComponent(); Tournament = new Tournament(); Tournament.PlayerList.Add(new Player("Hero", 5000)); Tournament.PlayerList.Add(new Player("Villain1", 3000)); Tournament