I've been creating an API and I'm now stuck on callbacks. There are many APIs that allow callbacks to class members(e.g. Windows API) using a void pointer to the object. I've searched the internet for hours and I can't find one example of how to use the "hidden object parameter" of an class method pointer that doesn't use std::function/bind or boost::function/bind. Any information on how API's like Windows API are able to use class methods as callbacks
when vpStatus is nonsense and unknown, the vaporPressure should not have a value; and if I calculate out a value for vaporPressure, the vpStatus can be set as known.
I am wondering if there is any set, pair or other structure can hold this two members together, so that when I change one's value, the other guy will also change accordingly.
The reason that class members are private by default is because, in general, an object of a class should be a self-contained entity such that the data that make the object what it is should be encapsulated and only changed under controlled circumstances. Public data members should be very much the exception. As you’ll see a little later in the chapter, though, it’s also possible to place other restrictions on the accessibility of members of a class.
I have a little problem with template classes and their specialization. Here is a short example:
template <typename T> struct A{ // some typedefs
[Code]....
The above example is not compiling, because of the assignment of the const static double. Double needs a constructor, but that doesn't work (or seems not to work) with static.
I'm not sure, if it works at all in C++ that way. All I want is a template struct with some typedefs and a constant which is different for different specializations. Don't think it has to be static, but that would be better style, wouldn't it?
I am doing C++ data structures exercises, and I am still learning some of the more basic concepts. I have a parent class:
template<class T> class linkedListType { public: protected: int count; nodeType<T> *first; nodeType<T> *last; private: };
Derived class:
#include "linkedListType.h" template<class T> class orderedLinkedList: public linkedListType<T> { public: void mergeList(orderedLinkedList<T> &list1, orderedLinkedList<t> &list2) { first = list1.first; ... } private: };
There is more code in my mergeList() function, but I included the line that is giving me problems. The error that my CodeBlocks compiler is giving me is that 'first' was not declared in this scope.
Strangely enough, if I change it to this->first, the error disappears.
1. Why does it not recognise 'first'? 2. Why would this->first work at all? Is the 'this' object a smart pointer?
I'm trying to put file data into members of a class. Remember to type in the file name you want to open. Cool feature right? I just had Dbase.txt so I chose that.
Fixed stuff in the .txt. Now I need to figure out why it only does 1 set and then ends.
#include <cstdio> #include <cstdlib> #include <iostream> #include <fstream> using namespace std; class INFO {
[Code] .....
Dbase.txt: Bob Guy Programmer M 9999.99 40 ------------------ Little Guy Little Brother M 0.0 3 ------------------
Im trying to make a c++ program for a school project, and i need to store the information into binary files, but I'm having some problems trying to store a class with string members, for example:
class whatever{ protected: string name; public: (List of functions) }
But if I do that, my code just dont work when I write and read a binary file, but if I change the string to char array, for example:
class whatever{ protected: char name[20]; public: (List of functions) }
It works good, so I wanted to know if there's some way to store a class wiht strings in binary files, or what am I doing wrong?
#include <list> #ifdef TICKABLE_EXPORTS //Automatically defined by MSVS #define DLL __declspec(dllexport) #else #define DLL __declspec(dllimport) #pragma comment(lib, "Tickable.lib") #endif
class DLL Tickable{
[Code] ....
error LNK2001: unresolved external symbol "private: static class std::list<class Tickable*,SKIPPED BITS> Tickable::subs" HUGE_SYMBOL_LIST PATHTickable.obj
I know with such a tiny and insignificant class the dll export seems pointless but this class is actually intended to be a .lib ONLY. But it is derived from by .dll style classes, and through inheritance this error is the exact same as what appears in the derived class, I just imagine that the cut down version would be easier to work with.
Is it possible to hold either a static variable in a dll which is of a dynamic type, OR would it be possible to reference an external variable which is static throughout the instances and this variable can be chucked away in a namespace of mine somewhere?
I suppose my only other option (if this is possible) would be to define a maximum instance number and create a standard array of pointers but this could both waste so much memory when not in use and cause problems if I need more memory.
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?
If I have an array of some class, and that class has const members, is there some way I can call a custom constructor on elements of the array?
I can't seem to reinitialize an element in foos in the example below. A thread on stack overflow mentioned the copy constructor show allow it, but I get "no match for call to '(Foo) (Foo&)'" when I try it.
"A nested class has free access to all the static members of the enclosing class. All the instance members can be accessed through an object of the enclosing class type, or a pointer or reference to an object."
How can the members be accessed through an object of the enclosing class type? I understand the pointer and reference part because for them you dont need the full definition, but for creating a object you do?
Also it has free access to all static members because the nested class is part of the enclosed class and with static it exists in everything inside the enclosing class? Right or am I missing something?
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:
A static function can be called in relation to a particular object by a statement such as the following:
aBox.Afunction(10);
The function has no access to the non-static members of aBox. The same function could also be called without reference to an object. In this case, the statement would be:
CBox::Afunction(10);
where CBox is the class name. Using the class name and the scope resolution operator tells the compiler to which class Afunction() belongs."
I am trying to input a call by value in the second class. It will not compile with how it is currently and says that the pounds needs to be a different variable. Why is this? Is this close to a call-by-value or am I way off?
#include <iostream>; using namespace std; int main() { int a, b, c, d; cout << "Please enter your weight in Pounds and Ounces ";
I'm having this pain in the ass error (No matching function for call to Data::Data() ) on this block of code:
Etapa::Etapa(string nm, float dist, string loc, Data dt) { nome = nm; distancia = dist; local = loc; data = dt; }
[Code].....
I guess this is happening because I'm trying to give Etapa an argument of Data type and I can't do it or put it in a variable since it has 3 parameteres (mes, dia, ano).
I created class called students which suppose to store students names of any sizes in an arrey but when I call the display function it does not show the names.
#include <iostream> #include <sstream> using namespace std; const int SIZE=5; class students{ public: string names[SIZE];
I have read the book over and over and I thought I understand "CLASS". But when I applied it and write the code the compiler tells me that there is a compiling error.
1. I have this method addProduct(Product* pProduct) in a Class called ProductRack, the code is in ProductRack.cpp file. The declaration of the Class methods and private variables are in ProductRack.h header file.
2. But when I call a method in the DeliveryCHute Class from the ProductRack Class I get a compiler errors which are these:
A.IntelliSense: a nonstatic member reference must be relative to a specific object B.error C2352: 'Project1::DeliveryChute::insertProduct' : illegal call of non-static member function
And this is causing the error:
if (Project1::DeliveryChute::insertProduct(pProduct) == false)
//THIS IS JUST ONE METHOD INSIDE ProductRack.cpp bool Project1::ProductRack::addProduct(Product* pProduct) { // Todo : Implementing if (Project1::DeliveryChute::insertProduct(pProduct) == false) return true;
I'm trying to implement Tarjan's Strongly Connected Components Algorithm in C++. Here's how I gotten so far:
void tarjan(vector<Vertex>& G){ index = 0; while (!S.empty()) S.pop();
[Code]....
Here's an example graph for the algorithm to run: [URL]
Here's the first part of the output of the program: [URL]
all the index & lowlink values of the nodes are set to -1 in the beginning. global index value is set to 0. My problem is, the algorithm starts running on Vertex X-4. It runs the instruction X-4.index=0 & X-4.lowlink=0 then it calls itself with the paramater of node X-1. it sets X-1's index & lowlink values to 1. then it calls itself for X2. then it checks whether node X-4 has the index value <0 or not. Even though we set the value of X-4 to 0 in the first run, it still sees X-4.index as -1.
