C++ :: How To Access A Specific Protected Inherited Member Depending On Class
Dec 30, 2013
I have `MainShop`(base class) then `SwordShop` and `BowShop`(derived classes) and another derived class called `Inventory`. I have a vector under protected in my base class, and when I access it from my derived classes it's okay, but each one has its own value. How can I set them all to have the same value?
//MainShop.h
#pragma once
class MainShop {
private:
//some variables
protected:
vector <string> WeaponInventory;
[code]......
Here every time I run it, it goes straight to the `else` and it displays that I do not have any items. I want to just have one vector for both my bow and Sword shops because vectors take up a lot of memory and my teacher said keep them to a minimum. So I just want one vector that takes in items from my bow class as well as my sword class, but for some reason it's acting as if I have multiple vectors, each with its own set of items.
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Oct 22, 2014
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?
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Mar 30, 2013
how to access the private and protected member functions of the class.....
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May 19, 2013
I understand what a map is and all, but what purpose does multimap serve?How can you access a specific member if the keys are the same?
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Sep 4, 2014
So I have an ImageManager class, Board class, and Box class. In Board.h I can declare ImageManager imgr; and in Board's constructor I can use imgr and its functions and such. However, in Box.h when I try and declare ImageManager imgr; I get the error "cannot access member declared in class ImageManager". Both declarations are under private, and exactly the same, but one doesn't work. Also, is there a way to only have one instance of ImageManager?
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Jan 10, 2015
I have the following scenario :
Code:
class test {
public :
int num;
};
int main() {
test t1;
test *ptr = &t1;
int test :: *mem_ptr = &test::num;
}
I need to access mem_ptr (pointer to a class member) through :
a. object (t1)
b. pointer to the object (ptr).
How can i do that ?
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Oct 24, 2013
This question is more from a design point-of-view rather than coding it to be a fully functional.
So here it goes:
I have multiple files which each require their own object of same class type (ref. First Class). File contents are read from a file to a unordered_map<std::string, std::vector<std::string>> which is either private or protected member inside First Class. First Class does not need any public functions to add, remove or change the data during runtime, but changes are only being made by checking if the file size has changed during the day, if the size is not equal to the last check, map gets updated.
Now, I have a Second Class which is a data handler class. It has public member functions with arguments that needs to be get from First Class's unordered_map using const_iterator. Which way to go with design and implementation.
I know there's two methods to do this. Re-doing handler class is also not out of the question. These two methods I'm aware of are:
1. Declare these maps to local scope, build few global functions and here we go. (Probably the easiest way.)
2. Create public member functions to a First Class which either return a pointer or a reference to a protected/private member. (I'm under the impression that I really shouldn't be doing this because of a bad coding practice.)
Note that I don't need any code here, just some other point-of-views regarding the subject itself for learning better coding practices.
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Jul 5, 2013
I have some doubt regarding class data member accessing in another file.Follwing code showing error.
class A://file a.cpp
{
public:
int add;
int sub;
};
//file b.cpp
extern class A
void cal()
{
A::add=A::sub;
}
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Oct 14, 2014
I mainly code plugins for Cinema 4D .... I used to code in COFFEE (a javascript like language, only for Cinema 4D) and python. But, recently, I started coding in C++.
I start my development on a Mac, using Xcode. But then, to generate Windows versions of my plugins, I take my source code to Visual Studio, perform the necessary adjustments, and create Win32 and Win64 code.
Lately, I was trying to devise a scheme to protect my plugins from being pirated. Yes, I know it is virtually impossible, but if I could make it harder for hackers to crack my plugins, it would be fine.
I made it work fine in python and in C++, but only in Xcode.
In Windows it is difficult. I only need to be able to access a username/password protected folder in my server and check if there is a file there. I don't even need to read the content of the file (but it would be nice to be able to do that too).
I started out using the cURL library but it is so complicated to make it work. I need 32 and 64 bit versions. Then I also have to include three .dll files in the folder of the application (that means that I would have to ask to the people who buy my plugins to copy three additional files to the main application folder... not a good thing )
So, any way to access a username/password protected folder on the net? (the username/password is generated in my code so, of course, I know what are the username/password to provide).
Also, I would need a way for the code to be completely self-contained, meaning that the users would not have to manually add any other files (libraries), besides the folder containing my plugin.
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Aug 22, 2013
I have a method:
int filetodb(std::wstring szwf, SQLHANDLESTR *h);
I want to use it, in a thread.
std says, use thread, as:
std::thread second (bar,0); // spawn new thread that calls bar(0)
How can I do this, for my method, that uses more than one, i.e., two, parameters?
My code is:
std::thread thread = std::thread(filetodb, filesP->at(i), h);
compiler says:
Error10error C2248: 'std::thread::thread' : cannot access private member declared in class 'std::thread'c:program files (x86)microsoft visual studio 11.0vcincludexmemory06061ConsoleApplicationa
How, can I do this?
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Feb 28, 2014
Suppose I make a class, something like having the constructor being invoked first makes sense, I don't have a problem with that. But, how could I limit access to functions until certain functions are called? Perhaps this isn't built into the language so you can't. And maybe this problem never comes up. For example if you have a set() and get() functions, if they are both public functions, there doesn't seem to be a way for the compiler at least now if set() never gets called you shouldn't call get(). I just see this as error prone if you need to use libraries, you have to know not to do it from documentation instead of something the compiler can check.
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Dec 4, 2014
I need to set signal handler for my process. As the signal is related with the process on system level I have faced the problem. My program consists several classes. They are connected together. But it doesn't metter in this case. The problem is that I need to access to member and methods of the class from my signal handler. For instance , I have class named Foo at it has some members and methods.
So from my handler I need to call its function and change members. I understand that compiler should know that this class instances will exist during all program execution. I have tried to set static member class Foo instance in another class , but this didn't solve the problem. How to correctly implement signal handling in such case.
Here is example of my code
class MyContainer {
private:
std::vector<Foo> container;
public:
int removeFromContainer(Foo* aFoo) {
[Code] ....
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Feb 25, 2013
When I put boost::thread Thread; in my struct I get the error error C2248: 'boost::thread::thread' : cannot access private member declared in class 'boost::thread'
The whole struct is
struct Player {
bool key[256];
char nameString[64];
bool lMouseButton;
bool rMouseButton;
double mouseX;
double mouseY;
[Code] ....
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Apr 1, 2014
I am currently doing the assignment about linked list. Here are some details information about what I am doing.. This program is C++ and should run on Visual Studio 2010. And it contains three file, two datastructure header and one main cpp file.
This program is trying to arrange and show some sports records. The main program which contain the functions such as reading the result text file(each result text file contain several records of athletes), removing a file, arranging the totalresult and printing it out. And the main program is already given and I cannot overwrite it.
But when I finished and try to build the solution and run it, I am not able to run the program and it give me somethings like these...
warning C4172: returning address of local variable or temporary
error C2248: 'Datastructure1::Datastructure1' : cannot access private member declared in class 'Datastructure1'
see declaration of 'Datastructure1::Datastructure1'
see declaration of 'Datastructure1'
This diagnostic occurred in the compiler generated function 'Result::Result(const Result &)'
And I have tried to comment each function part of the header file and see if can run or not. But I still fail to do so. Here are my codes...
#ifndef DATASTRUCTURE1_H
#define DATASTRUCTURE1_H
class Datastructure1 {
Public:
Datastructure1( );
[Code] ....
There are two header files and look quite long. They are all some linked list functions . I have read and learn linked list data structure before I complete this programs. However, when I complete the functions required, the function cannot be compile....
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Feb 15, 2013
this is my header file
#ifndef Header_H
#define Header_H
#include <iostream>
#include <string>
using namespace std;
class CurrentAccount{
[Code] ....
The problem i m facing now is the CurrentAccount class display is showing error inherited member is not allowed....
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Dec 4, 2014
I am writing my program on C++ language. I have one promblem. I need to set signal handler for my process. As the signal is related with the process on system level I have faced the problem.
My program consists several classes. They are connected together. But it doesn't metter in this case. The problem is that I need to access to member and methods of the class from my signal handler. For instance , I have class named Foo at it has some members and methods.
So from my handler I need to call its function and change members.
I understand that compiler should know that this class instances will exist during all program execution.
I have tried to set static member class Foo instance in another class , but this didn't solve the problem.
What is correct approach to do this. How to correctly implement signal handling in such case.
Here is example of my code
Code:
class MyContainer{
private:
std::vector<Foo> container;
public:
int removeFromContainer(Foo* aFoo) {
[Code] .....
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Mar 17, 2013
I have CAN Dll program for my application,which was separately used.Now I have included the Drivers program into my application Program and I am having this error System Access Violation Exception:Attempted to read or write protected memory.i am attaching the Dll code and Application code which is throwing this error.
[CODE]
The CAN Dll Code
int receive_data(unsigned char *data_output, int *MsgId, XLportHandle g_xlPortHandle){
XLstatusxlStatus, xlStatus_new;
XLevent xlEvent;
unsigned intmsgsrx=RECEIVE_EVENT_SIZE;
char *local_data ="11111111";
DWORD status;
xlStatus_new = xlSetNotification(g_xlPortHandle, &h, 1);
[code]...
My Application Code which is the receiver thread for accessing the messages got onto the CAN bus.
DWORD WINAPI Rcv_Msg(LPVOID param){
int*MsgId = new int;//msg id from CAN
intRcvVal;//0 = there is data in the queue; 1 = there is no data
unsigned int uMsgId;
*MsgId = 0;
unsigned char CanData[8];
[code]...
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Oct 24, 2014
I don't understand why my compiler gives me this error when I'm trying to run this code:
Code:
#include <iostream>
#include <cmath>
using namespace std;
class Airplane
{
public:
Airplane();
~Airplane();
[Code]...
The variable is protected. Yeah, that's right. But shouldn't a derived class be able to reach it? Or is it only in a function that the derived class is able to reach protected variables and isn't able to reach protected variables in the constructor?
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Jun 2, 2013
So i am having troubles with operator overloading in inherited class. Basically, it doesnt work. Consider this:
Code:
class A {
public:
A() {
x=0;
z= new int;
[Code] ....
Some how the copy constructor of a is improperly executed - the pointer is copied over, not re-created. As a result, the destructors crashes due to double-free.
*/
B bb = b; //doesnt work
B bbb(b); //doesnt work
B bbbb(b, 0); //works
}
Above code shows the problem well. The "official" copy-constructor wont work - it copies over the pointer directly, and doesnt create a new one as it should. However, if i provide my own pseudo-copy-constructor that works. But ofcourse it's just a cheap work around - and wont actually work in real code (STL).
compiler is VS2008SP1.
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May 1, 2013
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] ....
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Jun 18, 2013
I have three classes 1 base and two inherited.. problem is when I try to initialize the it says undefined reference to vtable constructor.
Code:
#ifndef QUOTE_H_INCLUDED
#define QUOTE_H_INCLUDED
#include <string>
using namespace std;
[Code] ....
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Apr 25, 2014
I have the following problem on my C++ Program and I am not sure why it is not working. I am creating a infix to postfix program through an inherited class which I am not sure it is working.
#include <iostream>
#include <stack>
using namespace std;
int in_stack_Priority(char a){
if(a == '*' || a == '/')
return 2;
[Code] .....
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Apr 30, 2013
how to create a base class that is derived (inherited) by three other classes?
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Jan 13, 2015
Here's the problem I want to intialise different classes based on user input. I've tried using an IF statement but the scope of an if statement would mean the rest main program wouldn't be able to see it.
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Jan 31, 2013
I need to create a GlobalConfig class. But I want to derive from it in another class.
Here's an example:
public class BaseConfig {
public string GlobalPath {get; set;}
}
public class ConfigA : BaseConfig {
public string pathA {get; set;}
}
public class ConfigB : ConfigA {
public string pathB {get; set;}
}
The idea behind is that I don't want to write the code multiple times and what's more important in class ConfigA I want to set GlobalPath and have access to it in ConfigB.
In other word I want class ConfigB to have a property GlobalPath which was set in class ConfigA.
To clarify I want to have only one object of Config in memory.
When I set BaseConf.GlobalPath to 'A', I want to access it from ConfigB.GlobalPath and also get 'A'.
I always design GlobalConfig as a static class, but static classes can't be inherited. So I tried to implement Singleton Pattern, but ConfigA can't find constructor of class BaseConfig because it's private.
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Jul 8, 2012
is there a way to have a template class respond to missing stuff in a template type ?
Code:
template <typename Type>
class MyClass
{
public:
enum { ID = Type::ID }; // revert to 1 if Type::ID doesn't exist.
};
If the Type passed to the template has an ID member (required to be an enum or a static const int), use it, if it is missing revert to a default value.
I can use this as a simplified way of configuring how MyClass works, without requiring Type to explicitely needing to define what it doesn't care about.
It needs to be resolved at compiletime, as it determines the number of elements in member array variables.
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