virtual

C++ pure virtual multiple inheritance?

由 一笑奈何 提交于 2019-12-22 03:48:43
问题 I need help for an implementation that uses multiple inheritance of Interfaces... There is an existing code whith an interface which has a lot of functions. The instances are created using a factory. class IBig { // Lot of pure virtual functions }; And his inplementation: class CBig: public IBig { // Implementation } I Want to split the interface in multiple smaller interfaces, but it should stay compatible to the existing code for some time. Here is a sample of what I tried to do: class

Accessing a method from a templated derived class without using virtual functions in c++?

由 人盡茶涼 提交于 2019-12-22 01:31:05
问题 How do I get around this? I clearly cannot make the value() method virtual as I won't know what type it is beforehand, and may not know this when accessing the method from b: class Base { public: Base() { } virtual ~Base() { } private: int m_anotherVariable; }; template <typename T> class Derived : public Base { public: Derived(T value) : m_value(value) { } ~Derived() { } T value() { return m_value; } void setValue(T value) { m_value = value; } private: T m_value; }; int main() { Base* b =

C++多态性与虚函数

由 情到浓时终转凉″ 提交于 2019-12-22 00:51:33
　　派生一个类的原因并非总是为了继承或是添加新的成员，有时是为了重新定义基类的成员，使得基类成员“获得新生”。面向对象的程序设计真正的力量不仅仅是继承，而且还在于允许派生类对象像基类对象一样处理，其核心机制就是多态和动态联编。 （一）多态性 　　多态是指同样的消息被不同的对象接收时导致不同的行为。所谓消息是指对类成员函数的调用，不同的行为是指的不同的实现，也就是调用了不同的函数。 1）多态的分类 　　广义上说，多态性是指一段程序能够处理多种类型对象的能力。在C++中，这种多态性可以通过重载多态（函数和运算符重载），强制重载（类型强制转换），类型参数化多态（模板） ，包含多态（继承与虚函数）四种方式来实现。类型参数化多态和包含多态称为一般多态性，是用来系统地刻画语义上相关的一组类型;重载多态和强制多态性称为特殊多态性，用来刻画语义上无关连的类型间关系。 　　C++中采用虚函数实现包含多态。虚函数为C++提供了更为灵活的多态机制，这种多态性在程序运行时才能够确定，因此虚函数是多态性的精华，至少含有一个虚函数的类称为多态类。包含多态在面向对象的程序设计中使用很频繁。 2）静态联编 　　联编又称为绑定，就是将模块或函数合并在一起生成可执行代码的处理过程，同时对每个模块或函数分配内存地址，对外部访问也提供正确的内存地址。 　　在编译阶段就将函数实现与函数调用绑定起来称为静态联编

On Linux: We see following: Physical, Real, Swap, Virtual Memory - Which should we consider for sizing?

由 ◇◆丶佛笑我妖孽 提交于 2019-12-21 22:19:02
问题 We use a Tool (Whats Up Gold) to monitor memory usage on a Linux Box. We see Memory usage (graphs) related to: Physical, Real, Swap, Virtual Memory and ALL Memory ( which is a average of all these ). 'The ALL' Memory graphs show low memory usage of about: 10%. But Physical memory shows as 95% used. Swap memory shows as 2% used. So, do i need more memory on this Linux Box? In other words should i go by: ALL Memory graph(which says memory situation is good) OR Physical Memory Graph (which says

abstract method in a virtual class

由 ≯℡__Kan透↙ 提交于 2019-12-21 18:34:12
问题 I have a c# Class that has lots of virtual methods, some of these methods are essentially abstract ( they are fully implemented in subclasses and the base class is empty). To get it to compile i am throwing an InvalidOperationException in the base class with a comment on what should be done. This just feels dirty. Is there a better way to design my classes? edit: It is for the middle tier of an application that will be ran in canada, half of the methods are generic hence the virtual. and half

Tkinter generate and invoke virtual event between different widgets

由 喜夏-厌秋 提交于 2019-12-21 17:45:08
问题 during writing some simple gui app in tkinter I met some small problem. Let's say I have custom menu widget (derived from tk.Menu) and custom canvas widget (derived from tk.Canvas). I would like to generate event from menu callback function and invoke it in canvas widget. I need to do it that way because it future I would like to add more widgets which should react to clicked position in the menu. I tried to do it that way: custom menu: class MainMenu(tk.Menu): def __init__(self, parent): tk

Effective C++ 读书笔记之Part6.Inheritance and Object-Oriented Design

由 前提是你 提交于 2019-12-21 07:18:59
32.Make sure public inheritance models "is-a". 所谓的最佳设计，取决于系统希望做什么事，包括现在与未来。 需要解决的问题：其中关于两个assert都通过的地方有些疑惑。 总结： “public继承”意味着is-a。适用于base classes身上的每一件事情一定也适用于derived classes身上，因为每一个derived class对象也都是一个base class对象。 33.Avoid hiding inherited names. 总结： 第一，derived classes内的名称会遮掩base class内的名称。在public继承下从来没有人希望如此。 第二，为了让被遮掩的名称再见天日，可使用using声明式或转交函数（forwarding functions）。 批注： 转交函数就是在子类中的成员函数中跳转到父类的成员函数。仅仅是加了一层包装。 34. Differentiate between inheritance of interface and inheritance of implementation. 1）声明一个pure virtual函数的目的是为了让derived classes只继承函数接口。 2）声明简朴的（非纯）impure virtual函数的目的，是让derived

Adreno GPU SDK例程分析(1)

由 社会主义新天地 提交于 2019-12-21 07:07:02
一、简介 Adreno GPU SDK提供了非常完善的框架，我们可以通过制作出很多有趣的东西，在Sample路径下的实例中，也提供了大量的实例来向大家展示其强大的功能。那么在接下来，我将带领大家对这些例程进行分析和学习。 二、OpenGL ES例程分析 进入Sample下的OpenGLES文件夹，大家可以看到大量的实例： 我们选择Skining例程吧，进入后会看到Scene.cpp和Scene.h两个文件，我们理所当然会先看一下Scene.h，看下它里面都有什么。 此处定义了一个Shader结构体： struct SHADER_CONSTANTS { INT32 m_slotWorldMatrix; INT32 m_slotViewMatrix; INT32 m_slotProjMatrix; INT32 m_slotMaterialDiffuse; INT32 m_slotMaterialSpecular; INT32 m_slotMaterialAmbient; }; 另外还有一个包含了Adreno SDK的框架函数的类，它继承自CFrmApplication。详细对SDK框架有过了解的朋友都知道这几个函数： virtual BOOL Initialize(); virtual BOOL Resize(); virtual VOID Update(); virtual VOID

Force calling base class virtual function

由 做~自己de王妃 提交于 2019-12-21 07:04:10
问题 I have some events like this class Granpa // this would not be changed, as its in a dll and not written by me { public: virtual void onLoad(){} } class Father :public Granpa // my modification on Granpa { public: virtual void onLoad() { // do important stuff } } class Child :public Father// client will derive Father { virtual void onLoad() { // Father::onLoad(); // i'm trying do this without client explicitly writing the call // clients code } } Is there a way to force calling onLoad without

How to perform a Virtual Mouse click C# without using a mouse

由 自作多情 提交于 2019-12-21 05:42:10
问题 I'd like to perform a click in a windows application, without using the real mouse (so I can minimize it). Much like a bot would behave. How would I do this? 回答1: I think the function you're looking for is PostMessage [DllImport("user32.dll", SetLastError = true)] public static extern bool PostMessage(int hWnd, uint Msg, int wParam, int lParam); You can read more about it here on codeproject, and download a demo project, which sends keystrokes. This method posts messages directly on the input
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