im passing a vector of a class to a function of another class. But i cant access the data on the classes inside the vector.
Something like that:
class CDummy{
...
public:
string m_name;
[Code].....
Im creating the vector on main() and using push_back with a pointer to an initialized CDummy instance
I know that it is possible to pass a class instance to a function, but in my experience, if said function changes any variables of the class, they don't actually get changed. For example, we have class object, that has a member int number = 5. Lets say we have two functions, func1() and func2, which are not members of class object. If we pass object to func1() which, lets say, increases number by 5 (so now number = 10), at the end of that function number still = 5.
Is there a way to bypass this and have functions alter class variables permanently?
I know that I can pass variables by reference, but, in my experience, such a thing does not work with vectors (which I am also dealing with), so simple passing the desired variables by reference won't work.
I want to be able to do
someFunction(MyObject)
rather than
someFunction(MyObject.getWhatIWant())
I know I can do &MyObject, MyObject() and MyObject[0] by overloading operators but is it possible with just plain old MyObject?
this is assuming that I have no access to someFunction(), i.e, it cannot be modified.
I have in the past written code for templated functions where one function argument can be either a function pointer or a Functor. Works pretty straightforward.
Now I am in a situation where I am actually trying to pass a function pointer as template argument to a class. Unfortunately this does not work, I can pass the Functor class but not the function pointer. Below code illustrates the issue:
Code:
#include <string>
#include <iostream>
#include <sstream>
#include <cstdlib>
// For demonstration
const char * external_library_call() {
return "FFFF";
[Code] .....
The idea is to have the definition of the Record class simple and readable and have a maintainable way to add auto-conversion functions to the class. So the lines I commented out are the desirable way how I want my code to look. Unfortunately I could not come up with any way that was close to readable for solving this.
I am trying to pass a class as a type to a template class. This class's constructor needs an argument but I cannot find the correct syntax. Is it possible?
Here is an example of what I described above. I did not compiled it, it is for illustrative purpose only. And of course argument val of the myData constructor would be doing something more useful than simply initializing an int....
template <class T>
class templateClass {
templateClass() {};
[Code]....
My real code would only compile is I add the myData constructor:
myData () {};
and gdb confirmed that it is this constructor that get called, even with dummy(4).
I know what are pointer's and how to use them but there is one point i am not able to understand. Below is the example code
I understand everything in the below code except 1 thing why i am using pointer to base class object in vector int the main() Function?
Code:
#include <iostream>
#include <sstream>
#include <string>
#include <vector>
using namespace std;
// base class
[Code] ...
Here is the lines of code i want to understand.
Code:
vector<Employee*> employees;
employees.push_back(&emp1);
employees.push_back(&mgr1);
I know if i will not use the pointer base class function "virtual double grossPay" will be called for both base class object and derived class object and when i will use pointer with reference to the object because base class function is virtual it will look for same function in derived class and if available it will execute it.
How can a member function in my derived class call the same function from its base class?
View 1 Replies View RelatedSay I have 3 classes:
class Player {
public:
virtual func1();
[code]....
Say in my main class, I have a function fight(Player p1, Player p2) and I would like to do something like this in the fight function, given that p1 is the human and p2 is the computer:
//function fight()
fight(Player p1, Player p2) {
p1.func2();
}
//using function fight()
fight(human, computer);
When I compile the program, I got this: error: ‘class Player’ has no member named 'func2()' What can I do to allow p1 to call func2 inside fight()? I'm not allowed to use pointers as the parameter for fight() and have to use the signature fight(Player p1, Player p2).
So I have a base class, lets call it base. In base I have a virtual function called update(), update just couts "base" then I have a class derived from base called derived;
it has a function called update(), update just couts "derived" then I create a vector called Vec it's initialised like this:
std::vector<base> Vec;
then I add an element into it like this
Derived DerElement;
Vec.push_back(DerElement);
then when I type:
for (int i=0; i<Vec.size(); i++) {
Vec.at(i).Update();
}
It outputs:
Derived DerElement2;
DerElement2.Update();
and it outputs this:
#include <iostream>
#include <vector>
class Base {
public:
virtual void Update() {
[Code] .....
and this is it's output:
Base
Derived
Press any key to continue . . .
I am writing a program which is using SDL library. I have two different classes which one of them is Timer Class and the other is EventHandling Class.
I need to use some member functions and variables of Timer in some Eventhandling Class member functions, Although I want to define an object of Timer in int main {} and relate it to its member function that has been used in Eventhandling member function in order that it becomes easier to handle it, I mean that I want to have for example two objects of timer and two objects of Eventhandling class for two different users.
I do not know how to relate an object of a class from int main{} to its member function which is being used in another class member function.
Lets have it as a sample code:
class Timer {
private:
int x;
public:
Timer();
get_X();
start_X();
[Code] ....
I just wondering if a base class can call the overridden function from a Derived class?
Here's an example:
//Base Class H
class BaseClass {
public:
BaseClass();
virtual ~BaseClass();
virtual void functionA();
[Code] ....
So basically, when I am creating a new object of Derived class, it will initialize BaseClass and the BaseClass will call functionA but I want it to call the function overridden by Derived class.
I know that if I call newObj->functionA it will call the overridden function. Right now I want the base class to call the overridden function "this->functionA(); in BaseClass" during its initialization. Is it possible to do that?
I'm trying to write a simple Delegate class with a Bind() and Invoke() function. For now it only needs to support a void class function with no parameters. I've searched around and found quite a few exmaples, though, those class are heavily templated and I lose track trying to simplify it.
So far my code is following:
Code:
#include <windows.h>
class Test {
public:
void DoSomething() {
MessageBox(NULL, L"Test::DoSomething!", NULL, 0);
[Code] ....
The part I am having difficulty with is assigning &Test::DoSomething to the m_Callback variable.
&tObject::DoSomething works, yet _Callback which I pass &Test::DoSomething to does not work.
Also, why does the following line work:
Code:
m_Callback = &Wrapper<tObject, &tObject::DoSomething>;
When wrapper is like:
Code:
template<class tObject, void (tObject::*Func)()>
void Wrapper(void* Object)
Should it not be Wrapper<class-typename, parameter-1>(parameter-2) // This currently creates an error
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.
Basically, I have a base class called MainShop and it has 3 derived classes which are SwordShop, SpellBookShop and BowShop. I want the base class to be able to call a function from one of the derived classes but no matter what i do, it doesn't seem to work!
Here is my code:
#include "MainShop.h"
//BaseClass cpp
void MainShop::EnterShop(Hero& hero)
[Code]....
I have two other derived classes, but its basically the same concept. I have a function in one of the derived classes and i would like to call it from the base class. This is one my derived classes:
//SwordShop derived cpp
#include "SwordShop.h"
void SwordShop::soldierShop(Hero& hero)
{
/* some code here*/
}
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?
I need to create a class vector as a template and define operations on vectors.
And this is what I made.
#include<iostream>
using namespace std;
template<class T>
[Code].....
I'm trying to template the return type for this function (component), I've looked around for example code but there doesn't seem to be any exactly like what I want.
Entity.hpp
class Entity {
public:
Entity();
unsigned int id = 0;
Component& addComponent(std::string);
[Code] ....
Error : 'ent1.component<HealthComponent>' does not have class type
i'm trying to send a vector to a function however i am getting these errors
error: invalid initialization of non-const reference of type 'std::vector<sf::Texture>&' from an rvalue of type 'std::vector<sf::Texture> (*)(sf::Texture, sf::Texture, sf::Texture, sf::Texture, sf::Texture, sf::Texture, sf::Texture, sf::Texture, sf::Texture, sf::Texture, sf::Texture, sf::Texture, sf::Texture, sf::Texture, sf::Texture, sf::Texture, sf::Texture, sf::Texture, sf::Texture, sf::Texture, sf::Texture, sf::Texture, sf::Texture, sf::Texture, sf::Texture, sf::Texture, sf::Texture, sf::Texture, sf::T|
error: in passing argument 1 of 'int set_explosion_textures(std::vector<sf::Texture>&)'|
my relevant code is
//vector containing fighter explosion frames
std::vector<sf::Texture> f_explosion_textures(sf::Texture f_explosion_1, sf::Texture f_explosion_2, sf::Texture f_explosion_3,
[Code].....
The case is like
class B{
public:
somedata;
somefunction();
}
class A{
public:
data;
function();
}
in somefunction i want a pointer to current object of class A m new to c++
I am writing a raytracer, and currently I'm working on creating a bounding volume hierarchy to accelerate the process. To do this, I am first creating a vector that holds each of the objects in the scene, and passing this vector to the constructor for my BVH.
Code:
//in header
BVH_Node* bvh;
//in main raytrace function
[Code] .....
I am testing a scene that has only 2 objects, and so it goes to the size == 2 check. The first time it hits makeLeaf(), I segfault. I've used both gdb and valgrind, and of course it's a memory mapping error. gdb's backtrace tells me that the length of the vector I've passed in is -805305610 and the capacity is -21, and that it is inside my makeLeaf() function that the error occurs.
Here's the function:
Code:
BVH_Node* BVH_Node::makeLeaf(GeomObj* v){
BVH_Node* node;
node->obj = v;
node->isObj = true;
return node;
}
The segfault happens at
Code: node->obj = v;
If I run my raytracer without a BVH, the objList works perfectly.
I'm currently building a new data structures that will be used in monte carlo generators (and so will be constructed several million times) and I'm wondering what's the best way (computer-speed-wise) to pass the data to the constructor. I am currently doing it using references and passing arrays as pointers like this:
Code:
class particle{
public:
particle(double *ar,int &id):IDup(id){
for (int i=0;i<5;++i)
Pup[i]=ar[i];
}
int IDup;
double Pup[5];
};
I'm assuming that since using references has no need to create a temporary memory slot it's more efficient .....
As for the arrays: is there a way for me to pass them as reference as well? (not using c++11), I'm using arrays instead of vectors as much as I can because I assume that vectors, being more advanced data structures, would take more time to create.
I am trying to pass an object to an inherited clas by a constructor. I am having Cboard my board and i need to pass it to the object Cpawn.
Here under is my code:
main
Code:
#include<iostream>#include "Cboard.h"
#include "Cpawn.h"
#include "Cpiece.h"
void main(){
char location[50];
[Code] ....
I'm having trouble with passing a character array between functions of the same class. I have a function, buildGraph, that calls function getNextLine. The getNextLine essentially just retrieves the next line of an input file and stores it into a "char line[80]". However when I try to use "line" in my buildGraph function, it has nothing in it.
Here's my code:
Class
#define NUMNODES 10
using namespace std;
#pragma once
class Prog3Graph
[Code] ....
I have a function called,
App 1:
void GetImage(CImage * img) {
//Pass &img over socket to another app
}
App 2:
void DisplayImage() {
CImage * pImg = &img;
}
Is it possible to pass a class pointer as memory buffer across the socket? The above code is just an example. My question in general is, whether it's possible to pass any Classes pointer as a memory buffer across sockets.
I'm trying to pass the value of an object created from a class file to a function outside of the "Int Main" function in the main.cpp file. I've successfully created the object, I just want to pass it to a void function but I'm getting the scope error below. I'm not sure how to correct. I'm not having much luck with research either (static variables?).
error: 'TicTacToe' was not declared in this scope
main.cpp
#include <iostream>
#include <cstdlib>
#include "Signature.h"
#include "Gameplay.h"
using namespace std;
// Initialize array
char square[10] = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9'};
[code]....
I was trying to implement own vector class and wrote some code. Below is the code.
Code: #include<iostream>
#include<vector>
using namespace std;
template <typename T> class MyVector
{
T *mem;
int m_size,final_size;
public:
MyVector() : final_size(1),m_size(4)
{
[code].....
I have question on this function.
Code: myVecPush_back(T t){}
Here I was able to put elements upto any number of time, but I have allocated memory to only 4 elements in T *mem.
My question, why the program is not crashing when I tried to put elements more that 4?
Is since the variable is of type Template? Any specific reason for this?