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 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:
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 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.
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() {
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.
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.
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!
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:
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'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 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.
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'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
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?).