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Read effective C + + Bar 歀 09: Virtual functions are never invoked during construction and destructor (Never call virtual functions during construction or destruction)
First, we use a phrase that is popular with programmers as the beginning of this article: if you call a virtual
Description of the problem:Write a program. Defines the abstract base class shape, which derives 3 derived classes, Circle (circle), Rectangle (Rectangle), Triangle (triangle). Use the main () function such as the following. Find the area and the number of geometry defined.int main () { Circle C1 (12.6), C2 (4.9);//Create Circle Class object c1,c2 with radius Rectangle R1 (4.5,8.4), R2 (5.0,2.5);// Establish the Rectangle class object R1,R2, the
/** Copyright (c) 2013, School of Computer Science, Yantai University * All Rights Reserved. * file name: test. CPP * Author: Qiu xuewei * Completion Date: July 15, June 2, 2013 * version: V1.0 * input Description: none * Problem description: * program output: * Problem Analysis: * Algorithm Design: * // * design an abstract class csolid, which contains two pure virtual functions to evaluate the surface are
See stroustrup's answer (http://www.research.att.com /~ BS/bs_faq2.html # vcall)
Although calling a virtual member function in constructor is not a very common technique, studying it can deepen the understanding of the virtual function mechanism and object construction process. This problem is also different from t
class function, the C + + compiler does not control whether the class is empty, but instead passes the address of the class as the this pointer to the function.A->print (), it is equivalent to print (A) in the compilerThere are cases where member variables are not used in print, so it is natural to run correctly.Then look at the assembly code to get a better understanding of it. The following is the assembly code within the People class. 21 void e
;}Tale -> Act1 ();Delete tale;} Result AnalysisInput FPrincess meets FrogPrincess kisses frogFrog turns into PrinceThey live happily ever afterThe endWhen u is input, the result isPrincess meets FrogPrincess kisses frog // the above two sentences are determined by the inheritance relationship. Although unhappytale does not have void act1 () or void Act2 (), both of them are inherited from fairytale and act1 () is a virtual functionFrog stay a frog /
First, we give the base class animal and the sub-class fish.
==============================================================
// animal.h
///
begin : 2012-06-30
//author : Zwq
//describe: In the case of a non-virtual function, the child class pointer is assigned to the accumulating pointer to verify the final call
// base class
1. When a constructor is called in a subclass, its parent constructor is definitely called first. If there is a virtual function in the parent class constructor, and there is a subclass, it must execute the virtual function in the parent class, and the member variable in the subclass is not initialized, so the correspo
Although calling a virtual member function in constructor is not a very common technique, studying it can deepen the understanding of the virtual function mechanism and object construction process. This problem is also different from the general intuitive understanding. Let's take a look at the two class definitions be
the parent window is created and called in oncreate () when it is processed.
Function:
Control creation details
Cwnd implementation:
.......// Register the window class and call the API to create a window// Allow modification of several common create parametersCreatestruct Cs;CS. dwexstyle = dwexstyle;CS. lpszclass = lpszclassname;CS. lpszname = lpszwindowname;CS. Style = dwstyle;CS. x = X;CS. Y = y
You can, but do not achieve the desired effect, you should avoid calling virtual functions in constructors and destructors as much as possible.
Class base{public
:
base () {
cout
When you define a derived instance object, calling size () in the constructor of base is Base::size () instead of derived::size () by static resolution.
It can be understood that when the base part is constructed, the derived is not a complete instance objec
Item M12: Understanding the difference between "throw an exception" and "pass a parameter" or "call a virtual function"Syntactically, there is little difference between declaring a parameter in a function and declaring a parameter in a catch clause:Class Widget {...}; A class, specifically what class
First of all, for an inheritance system, the constructor is invoked from the base class, and the destructor is just the opposite, starting with the outermost class.
For a call to the virtual function in the constructor, give an example:
1 class Transaction //所有交易的基类 2 { 3 public: 4 Transaction(); 5 virtual void
Yesterday, when the written test encountered a very interesting topic, the general following:Classparent{public:parent () { doit (); }~parent () {doit ();} virtualvoiddoit () { coutThe case of calling virtual functions in a constructor was not previously written in the project, which is generally not allowed, increasing the complexity of the code (see effective C + + clause 9). Remember that the order of construction and destruction in C + + inherita
inheriting virtual function call codeThis address: Http://blog.csdn.net/caroline_wendyWhen a derived class inherits a base class , it is dynamically bound when using virtual , and is overwritten without the virtual keyword .When you use a base class pointer (base*) to point
[C/C ++ school] 0905-boostSocketTCPUDP/virtual function table call/complex expressionBoostSocketTCPUDP
Serverudp. cpp
# Include
# Include
# Include
# Include
Using namespace std; using namespace boost: asio; void main () {io_service io_serviceA; // a service class that initializes the ip: UDP :: socket udp_socket (io_serviceA); //
In C ++ (Base Class pointer) Call virtual functions
Association refers to a computer.ProgramThe process of self-Association. According to the different stages of association editing, there are two different association methods: static Association editing and Dynamic Association editing. During the compilation phase, the Compilation Program does not know exactly the fun
Environment: XPSP3 VS2005Today the black general to the candidate out of a C + + constructor call virtual function, the specific topic is more complex than the title, the general situation can see the following code:[CPP]View PlainCopy
Class Base
{
Public
Base ()
{
Fuction ();
}
virtual void fuctio
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