inheritance

问题 I have 2 classes, one MainWindow in which we draw in a QGraphicsView a circle (which intend to become a button !) created thanks to an other class. The class MyCircle inherits from QObject and QGraphicsItem since I want to make animation. My issue is the following : My goal is first to make a simple animation on my drawing : make it smaller then it goes back to the original size. So I suppose I should use the property geometry, already existing in the QObject class. To do this I write in my

问题 I have the following interfaces: Interface IViewModel ... End Interface Interface ISpecialViewModel Inherits IViewModel ... End Interface Interface IView WriteOnly Property MyViewModel As IViewModel End Interface Following are my classes: Class VerySpecialViewModel implements ISpecialViewModel ... End Class Class View Implements IView Public WriteOnly Property MyViewModel As VerySpecialViewModel Implements IView.MyViewModel ... End Property End Class It tells me that 'MyViewModel' cannot

问题 I have inherited exiting data from one form to another form using following coding xml: <field name = "res_model">lis.lab</field> python: _inherit="lis.lab" lis.lab is first form. I enter information and save only here. test.lab is another form. Here I have finished to display that record here(test.lab) in tree view using above two line click. But It has only exiting field in "test.lab" form. And it's not showing new field in second form(test.lab). xml <?xml version="1.0" encoding="utf-8"?>

问题 This question already has answers here : Closed 7 years ago . Possible Duplicate: Downcasting using the Static_cast in C++ I'm very confused by when do we need to convert pointer to base object into pointer of derived class? Can anyone do me a favor to give me some example? 回答1: What kind of conversion are you talking about? If it's about down casting (or dynamic casting , which is the same kind but it's verified at runtime) then you are allowed to do it to force the type checker to not check

问题 Trying to understand a question I got wrong on a test: How does inheritance differ from implementing interfaces? With inheritance, a class gains behavior from its superclass. With interfaces, a class gains behavior from the interface it implements. (this is the one I chose) With inheritance, a class must implement the methods defined by its superclass. With interfaces, a class gains both instance variables and behaviors from the interface it implements. The way I was thinking is that

问题 The following code gives the error: 'B' is an inaccessible base of 'D'. Why does this happen? The constructor of B is public which means it should be inherited by class D even though the inheritance is protected / private. Can someone tell me a workaround as well? Except of course making the inheritance public. #include <iostream> #include <typeinfo> using namespace std; class B { int i; public: B() { i=1; } int get_i() { return i; } }; class D: private B { int j; public: D() { j=2; } int get

问题 I am creating a simple bank account GUI , when i click the menu " interest" the variable changed from 1 to 2 , which should change the value of the current balance by 10 percent, however the value stays the same, give your insight. from tkinter import * from random import randint class BankAccount(object): def __init__(self, initial_balance=0): self.balance = initial_balance def deposit(self, amount): self.balance += amount def withdraw(self, amount): self.balance -= amount def get_balance

问题 I've got a tricky issue with "overriding" static arrays. I've got static arrays (for simplicity) that are of fixed length in different derived classes, but still all sizes are known in compile-time. I've also got a virtual function in the base class, but I don't know how to tackle the problem of overriding these arrays and array-sizes in the derived classes so that this virtual function works correctly, i.e. gives the sizes and array contents from the derived classes. Example: class B {

问题 I've been working on a basic class inheritance exercise, and even though I think I've got the jist of it, my program isn't working the way it should. I'm getting compile errors and haven't been able to figure out why- it'd be great if you all could help me out here. So to start off, there are three files 1. Person.java -base class 2. Student.java -a derived class of Person.java 3. Family.java -not quite sure, I think it's its own base class Person.java has two instance variables, String name

问题 Learning JS in codecademy, confused about some technicalities regarding inheritance on lesson 18/30. Penguin is a subclass of Animal. I set Penguin's prototype to Animal, and in the Penguin constructor I specified its numLegs. However, I did not specify its name and food, which are properties of the Animal class. The Penguin constructor only takes 1 parameter, name, whereas the Animal constructor takes 3: name, food, and numLegs. If I create a new Penguin object named "Bob", for instance,