polymorphism

问题 I am learning OOPs with python. created below code to replicate the diamond shape problem in multiple inheritence. I am running the below code in jupyter notebook and output is generated at same. class parent: def __init__(self): self.a=2 self.b=4 def form1(self): print("calling parent from1") print('p',self.a+self.b) class child1(parent): def __init__(self): self.a=50 self.b=4 def form1(self): print('bye',self.a-self.b) def callchildform1(self): print("calling parent from child1") super()

问题 Polymorphism for inputs was solved using functional idiomatic approach and now looking forward to solve it for return types that involved a JSON serializer which actually demands to know the type of the record. Input parameters were enforced to have some specific fields as mandatory and the solution allowed to pass different types as long as the field members existed. Solution was referred to as SRTP or structural (or duck) typing. Now I've a roadblock where this function is essentially a web

问题 I have a class // i want an abstract class. class Foo { public: virtual void bar()=0; }; // i want this abstract calss to be used all over the program :) to enjoy polymorphism. class EatFoo { public: vector<Foo> fooV; // not working vector<Foo *> fooPV; }; I get a compile time error that abstract class cannot be instantiated. Yes its true but i really want or i want to learn : how to make other programmers "have to - have to" implement some function and i donot want to use pointers in my

问题 I'm writing a game (space invaders) on an Arduino which is connected to a graphical LCD, and I have a sprite class. This class has attributes such as Player/Alien, a bitmap object, location(x,y), and a how to move function. I want each instance to have a missile and I think this may be done by inheritance and polymorphism, though I'm unsure how -- my streamlined code is below and to give a better idea as to shapes I've included a glyph image. I'd like Missile to derive location(x,y) from the

问题 I am trying to code an effective implementation of the following composite class: class composite{ vector<base_class *> Vec; //Other useful constants public: composite(vector<base_class*>); //Other useful operations... }; My question is about the constructor and instantiation of the class and in particular the object Vec. At the minute, I use the rather crude implementation outlined below. I the implementation to be memory efficient. I'm pretty much a newb with C++, so I'm not sure I have the

问题 I'm really new to JEE CDI but tried half of last night to find a solution to a problem. I have a Controller Class that, when startup is called, should inject a stateful bean using a Producer depending on a parameter. This mentioned stateful bean itself contains an injected bean itself. To be honest, not sure if this works at all, any feedback is highly appreciated=) Here is some dummy code that should help understand what I want to do (based oin https://docs.jboss.org/weld/reference/1.0.0/en

问题 I must implement an ObservableHashSet<T> that can quickly ( O(1) ) test for object existence: public class ObservableHashSet<T> : ObservableCollection<T>{ readonly ISet<T> _set = new HashSet<T>(); protected override void OnCollectionChanged(NotifyCollectionChangedEventArgs e){ base.OnCollectionChanged(e); if (e.Action == NotifyCollectionChangedAction.Move) return; if (e.OldItems != null) foreach (var old in e.OldItems.Cast<T>()) _set.Remove(old.GetHashable()); if (e.NewItems == null) return;

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 Consider these classes: Class A : public QObject { ... Q_PROPERTY(int value READ value WRITE setValue NOTIFY valueChanged) virtual int value() { return m_value; } void setValue(int v) { m_value = v; Q_EMIT valueChanged();} ... }; Class B : public A { ... int value() { return m_value * 2; } ... }; When property value is accessed, the Class A method is called directly instead of Class B's. So far, to workaround this apparent limitation I've replicated the property code and connected the signals

问题 In a previous question I asked how a record field can be made polymorphic when using DuplicateRecordFields. I got an excellent answer for this from @user2407038. He answered the question to my initial spec providing one type class per field, but he mentioned that it could all be simplified into one typeclass. (Note: this too can be generalized to a single class with an additional parameter corresponding to the field name; this is probably outside the scope of this question). I'm not sure how