In short, this is what I have
class A{
A(){}
virtual void pure() = 0;
}
[Code] .....
I need a2 to be a deep copy of a1, but if I understand it correctly, then a2 should just be a pointer copy of a1. How do I make a2 be a different instance of B?
I am facing a real-life problem, it can be simplified as below:
#include <iostream>
using namespace std;
class B;
class A {
public:
void f1(A a) {}
void f2(B b) {}
[Code]...
There is no problem at all with the f1(), it compiles and executes without any problem. But f2() gives compilation error. How to solve this?
The error message is: error: 'b' has incomplete type This is just to define the function f2() in a class, that uses an instance of its child class as one of its arguments.
I am currently having an issue with a piece of code that I am writing in which I need to use a vector of a child class as a parameter in a function in the parent class. Below is an example of my code:
#include "child.h"
#include <vector>
class parent {
parent();
function(std::vector<child> children);
// rest of class here
}
When I do this my program doesn't compile. However if I try to forward declare, as shown in the following example, it once again refuses to compile:
#include <vector>
class child;
class parent{
parent();
function(std::vector<child> children);
// rest of class here
}
This time, it refuses to compile because it needs to know the full size of the class child in order to create the vector. How to being able to access the child is essential for my program, so what should I do?
The compiler creates virtual table for the base class and also for the derived class whether we override it or not.
That means each class has separate virtual table. when we get the size of the each class with out any data members... the size of base is -- 4 bytes(64 bit) and the size of derived is -- 1
The size of base class 4 is correct since it creates the virtual pointer internally and its size is member data + virtual pointer, but it in this case I have included any data members so it has given 4 byts.
But why in case of derived is 1 byte, since it the derived class has overridden the virtual function from base, this will also contains the virtual pointer which will be pointing to derived class Vtable, it the size of the class suppose to be 4 instead of 1 byte.
#include<iostream>
class A{
public:
[Code].....
class Parent{
public:
virtual int width();
virtual int height();
int area(){return width()*height();};
[Code] ....
hiclass Parent {
};
class Child : virtual public Parent {
};
What is the size of object of Class Child in following case?
I am facing some problems while overloading base class functoin in child class. I have 2 programs as listed below.
Program 1 :
#include <iostream>
using namespace std;
class base
{
[Code].....
Compilation Errors:
child_overload.cpp: In function "int main()":
child_overload.cpp:27: error: no matching function for call to "child::func(const char [16])"
child_overload.cpp:17: note: candidates are: void child::func(double)
I thought as base class members are also as part of child class through "public" access specifier, it should access base class function, when funct() is called with a string. if I use "using base::func" in child, it works fine. But why I need that when base class memebers are part of child class?
We want a solution in C++ that must be able to do the following:
Given a string of particular type, lets say 'A', we want to find all the types that derives from 'A'.
Instantiate new objects out of the types that are derived from 'A'.
E.g. Lets say we have a class, VehicleEntity. VehicleEntityhas child classes, PassangerCarEntity, TruckEntity, TrainEntity, BoatEntity.
We are unsure what vehicle entities there may be as the a library could be added containing more VehicleEntities. E.g. an AirplaneEntity thaterives from VehicleEntity could be added after deployment.
In the application, when a user wants to select a VehicleEntity, the user should be able to pick any of the entities deriving from VehicleEntity. This includes the PassangerCarEntity, TruckEntity, TrainEntity, BoatEntity and AirplaneEntity. The user selects an Entity, lets say AirplaneEntity, A new object of type AirplaneEntity must be instantiated.
The following is an concept example in C# of what we want to achieve in C++.
In C# the items for the dropdown list can be retrieved as follows:
Type vehicleEntityType = typeof(VehicleEntity);
List<Type> types = new List<Type>();
foreach (Assembly assembly in AppDomain.CurrentDomain.GetAssemblies())
[Code] .....
We are aware that standard C++ does not contain any Metadata on its objects, and thus it is not possible without a workaround. It does not seem possible with RTTI and boost.Mirror.
I am trying to create a platformer and is stuck on a problem regarding my virtual class Entity. I wish to use it to create stuff like the Player and Enemy class(es). But how to do the parameter for my collision check function. Below is my Entity- and player class.
There might be a better way to check CC with a lot of different objects, this is my first attempt.
This is the error I am getting: "error C2664: 'bool Player::CollisionCheck(Hostile)' : cannot convert argument 1 from 'Player' to 'Hostile'"
#ifndef ENTITY_H
#define ENTITY_H
#include <SFMLGraphics.hpp>
class Entity {
public:
Entity();
Entity(sf::Vector2f position, sf::Vector2f size, sf::Color fillColor, sf::Color outlineColor);
[Code] ....
and in Hostile I would (I guess) use
bool CollisionCheck(Player p);
But if I try for example to use Player in the CC in player.h it will complain that the function doesn't have an overload for that. Hostile is just a example class name right now, it isn't implemented yet. I am trying to use Player, but if possible wish to be able to have a different class depending on what kind of entity it is. The entity will probably also be the players projectiles and so on.
I am making a very basic parent/child class based program that shows polymorphism. It does not compile due to a few syntax errors reading "function call missing argument list. Lines 76 and 77, 81 and 82, and 86 and 87.
#include<iostream>
using namespace std;
class people {
public:
virtual void height(double h) = 0;
virtual void weight(double w) = 0;
[Code] ....
The abstract class can provide more functionality without affecting child classes.If we add any method to the interface ,then will it affect all the child classes ?
View 2 Replies View RelatedI have this header file called Shape.h containing these function declarations. and a Shape.cpp which contains the body of the function. I am not showing it since it is not needed.
//This is from Shapes.h header file
#ifndef SHAPES_H
#define SHAPES_H
#include <iostream>
[Code]....
I have this unfinished Main.cpp because the third line "JuanSanchez::Circle *pCar = new Circle; " is giving me a compiler error "error C2061: syntax error : identifier 'Circle' "
#include "Shapes.h"
int main()
{
const int arrayIndex = 4;
JuanSanchez::Shape *myShape[arrayIndex];
JuanSanchez::Circle *pCar = new Circle;
}
What Could be causing this error?
How can I access the virtual base class? This is a practice exercise from c++ primer plus 6.
The problem is that the name becomes No Name instead of the name specified when creating the gunslinger, I don't know how I can call the virtual base class explicitly
Output,
#ifndef PERSON_H_
#define PERSON_H_
#include <string>
#include <iostream>
#include <cstdlib>
using std::string;
class person
[code]....
I have a 'Graph' class, which has derived classes for Adjacency Matrix and Adjacency List representations.
How do I provide iterators for traversing vertices and edges, when the iterator classes would have different implementations for the different derived classes ?
The following way is the only one I can think of, but seems quite cumbersome.
Code:
class Base {
public:
class BaseIterator {
};
virtual const BaseIterator& begin();
virtual const BaseIterator& end();
[Code] .....
Or is there a pattern for doing this that I'm not aware of ? Would composition be a better idea here compared to polymorphism ? I mean, I can think like..a Graph can 'have' several representation 'objects' within it.
All the involved classes are templates,not sure if that makes the situation different.
Below is simplified code consists of two classes, namely Parent and Child.
Child is inherited from Parent.
All member functions of class Parent are declared virtual, and they have been overridden in the class Child.
Code 1:
#include <cstdlib>
#include <iostream>
using namespace std;
#define QUANTITY 5
class Parent {
[Code] ....
The output of the code:
Child::showID() -- ID is 1804289383
Child::showID() -- ID is 846930886
Child::showID() -- ID is 1681692777
Child::showID() -- ID is 1714636915
Child::showID() -- ID is 1957747793
Parent::operator=() invoked.
Child::showID() -- ID is 1804289383
Child::showID() -- ID is 846930886
Child::showID() -- ID is 1714636915
Child::showID() -- ID is 1714636915
Child::showID() -- ID is 1957747793
Question:
Why is Parent::operator= invoked instead of Child::operator= ..?
Isn't it already declared virtual and hence would be overridden..?
I need to invoke Child::operator= instead. How to achieve this?
Here is an example,
Code:
class A {
public:
virtual void foo(){}
virtual void foo2(){}
virtual void foo3(){}
};
int main() {
A a;
int ret = sizeof(A);
return 0;
}
Basically object a contains a virtual table pointer which is of size 4 bytes. Since class A should have a virtual table which contains three pointers pointing to foo, foo2,foo3 separately. So the virtual table should be of size 12 bytes. I wonder where is virtual table located in memory?
I develop add-ons for MS Flight Simulator and I use the poorly documented SDK for this. The SDK provides a .h file in which an interface class is defined (with pure virtual methods only), something like this:
Code:
class IPanelCCallback {
public:
virtual IPanelCCallback* QueryInterface (PCSTRINGZ pszInterface) = 0;
virtual bool ConvertStringToProperty (PCSTRINGZ keyword, SINT32* pID) = 0;
virtual bool ConvertPropertyToString (SINT32 id, PPCSTRINGZ pKeyword) = 0;
};
In my code, I use this interface like this:
Code:
IPanelCCallback* pCallBack = panel_get_registered_c_callback("fs9gps");
...
SINT32 id;
pCallBack->ConvertStringToProperty(propertyName, &id);
Everything works fine, but I don't understand why... I thought the linker would stop with an "undefined symbol" error because the IPanelCCallback methods, such as ConvertStringToProperty, are declared as pure virtual but defined nowhere, and I don't use any library for linking. With such an interface class, I thought I would have to defined a subclass of IPanelCCallback and define the ConvertStringToProperty method.
Assume this class:
class GenericTrafficLight {
public:
virtual enum LightState;
void setLightState(LightState newState) {
currentState = newState;
}
private:
LightState currentState;
};
And this deriving class:
class FuturisticTrafficLight : public GenericTrafficLight {
public:
enum LightState {
LIGHT_STATE_RED = 0,
LIGHT_STATE_YELLOW = 1,
LIGHT_STATE_CYAN = 2,
LIGHT_STATE_GREEN = 3
};
};
This yields this error: "C2911 (...) cannot be declared or defined in the current scope" in the deriving class's enum definition.
Let's look at this simplified code, it gives compilation error
#include <iostream>
using namespace std;
class A {
public:
void showInfo() { cout << " This is an instance of A" << endl; }
[Code] ....
Without using pointer, how to make this works?
I'm doing a 1Mb memory dump like this:
Code:
for (int i = 0; i < 0x00100000; i++) {
dump[i] = *(chipmemory+i);
} // i
Then I save the 1Mb "dump" array to a file, and the file contains the data I expect.
The problem arises when I try to write data back to the array beginning at the "chipmemory" pointer:
Code:
unsigned char msga[18] = "SOME MODIFIED DATA";
int address = 172378;
for (int i = 0; i < 18; i++) {
*(chipmemory+address) = msga[i];
address++;
} // i
Is this the correct way to write back to an address 172378 bytes from the "chipmemory" pointer? or is my code broken somewhere else?
I have declared two vectors:
std::vector<Class 1> object1;
std::vector<Class 2> object2;
object1 has some value which I want to copy in object2? Is it possible to do?
How to make a C function, that will be copying string to the clipboard?(so during execution it copies to cliboard, and after the program ends its execution I will be able to do "Ctrl-V" and paste the things copied)?.
I assume that linux have some sort of in-kernel clipboard which can be filled with some systemcall?
how I would code copying a file that cannot be opened (eg. any file that isn't ANSII format).
I know that for a .txt or something like that I could simply do
#include <iostream>
#include <fstream>
#include <string>
[Code].....
how I would copy a file's contents into a char buffer and copy it over to another file for files that can't be opened/read in notepad? (Example: a rar file or a .exe ) Not sure if that makes
I'm having some trouble with copying one I/O stream into another. I've put the first one into an array but I cannot get my second prompt to copy the .txt file the first prompt sees and outputs to the console. When I try and grab the info from the .txt file my first prompt sees I only see blank space in my .txt file.
#include <iostream>
using std::cout;
using std::cin;
using std::endl;
#include <fstream>
using std::ifstream;
using std::ofstream;
[Code] .....
I'm trying to make a program that will copy all files from one folder in to another folder.
Ex path:
From: G:ExExF1
To: C:EXAll
I'm using Visual studio express C++ as the IDE. I have tried using this code:
bool copy_functions::CopyAll(string InPath,string OutPath) {
ifstream In(InPath.c_str(),ios::in|ios::binary);
ofstream Out(OutPath.c_str(),ios::out|ios::binary);
[Code] ....
But I always get booth could not be opened for copying messages even thug I use the absolute paths for the folders.
So I'm writing a function isPalindrome() that can accept a string as an argument, and copy from it only the alphabetic characters in the argument (original) string to another string named alpha_array which contains only the alphabetic characters. Then the function should be able to call the isPurePalindrome function to determine if alpha_array is an ordinary palindrome.
The problem is that when I call isPalindrome in main, the program crashes.
Here's the code I have for isPurePalindrome and isPalindrome:
Code:
/* 1 */
int isPurePalindrome( const char * sentence ) // Can accept strings, array and pointer arguments
{
// Declarations
[Code].....