In object-oriented programming to allow access to "private" or "protected" data of a class in another class, the latter class is declared as a friend class.
Questions tagged [friend-class]
83 questions
3
votes
3 answers
Understanding member access with inheritance / friend class in C++
from C++ primer 5th edition:
have a look at these classes:
class Base {
friend class Pal;
public:
void pub_mem();
protected:
int prot_mem;
private:
int priv_mem;
};
class Sneaky : public Base {
private:
int j;
};
class Pal…
Jason
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3
votes
2 answers
Defining an stl container for a class that has just been declared.
I am trying to implement a finite element code for my research. I need to create a map that associates materials with their names so that I can access them by name.
From the header file of the main class, I define the following:
/// Friend class…
Subramanya Sadasiva
- 113
- 6
2
votes
1 answer
C++ detail namespace vs anonymous vs private method to class vs. pimpl vs. friend class
Bear with me here.
I am trying to figure out at what point do you draw the line regarding putting helper methods in anon vs. detail namespace vs. private vs. creating pimpl or friend class.
Here's my take.. Please let me know your thoughts.
So,…
thassan
- 391
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2
votes
1 answer
C++: how to make a group of derived classes be able to access private members of one class?
Suppose a class: Library
And we have a group of derived class from the base class LibraryCustomer, such as:
Kid, Parent, Student,
etc
In the class of Library, there are a group of (tons of) private members variables.
Since there are tons of private…
user1914692
- 3,033
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2
votes
1 answer
Friends and nested classes
Ok I'm totally frazzled on this. Code is begin to swim around the screen...must sleep.
So! Ok, troubled by nested classes and friends.
here is the pseudo-code
class A{
public:
//constructor
// member functions
…
A Big Ball Of Lettuce
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2
votes
1 answer
friend class with forward class declaration does not compile
This a basic program to understand how to use friend class in C++.
Class xxx has a class yyy object using friend. Since class yyy
is defined after class xxx I have declared class yyy using forward
declaration.
#include
using…
Santosh Sahu
- 2,134
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2
votes
2 answers
Access Mysql * connection variable from different c++ class
I wrote c++ class to connect to mysql database:
hpp file
#include
#include
#include "mysql/mysql.h"
#ifndef _DATA
#define _DATA
class Database {
public:
string host;
string user;
string pwd;
string db;
…
Begayim Muratalina
- 621
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2
votes
2 answers
Using friend function in C++
Just read about friend functions and I'm trying to access private variable "number" in class A with friend function "Print" from class B. I'm working with Visual Studio. Compilation of my code gives me plenty of various errors like:
C2011: 'A' :…
QED
- 77
- 1
- 8
2
votes
6 answers
Why we need a "friend" here? (C++)
The qml viewer (for 4.8 and 5.0) is implemented like that:
In the .h(eader) we have:
class QtQuick2ApplicationViewer : public QQuickView
{
Q_OBJECT
...
private:
class QtQuick2ApplicationViewerPrivate *d;
};
Then in the .CPP file:
class…
Zingam
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1
vote
2 answers
friend class doesn't do well with me?
I am trying to deal with friend class for the first time. I wrote the code below:
class Kind{
private:
friend class Type;
int x;
public:
Kind(){ x=0; }
void setX(int X) { x =X; }
int getX() { return x; }
};
class Type:…
Aan
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1
vote
1 answer
How to declare a template friend class inside other template class?
Hello. I'm trying to implement double linked list. I have a linked_list class and DListNode class as a shell for elements in my container and I prefer DListNode as a class rather than as a struct, because I want node fields to be inaccessible…
getsuga
- 15
- 5
1
vote
2 answers
Can't access private constructor from a friend class
In the following code snippet, g++ compiler outputs the following error:
error: ‘B::B(const string&)’ is private within this context 857 |
{ return unique_ptr<_Tp>(new _Tp(std::forward<_Args>(__args)...)); }
Commenting out the line where smart…
Hossam Elsamanoudy
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1
vote
5 answers
Why does friend class crash on static function call?
#include
using namespace std;
class CClass
{
private:
friend class CFriend;
static void privateFunc(){std::cout << "privateFunc" << std::endl;};
};
class CFriend
{
public:
void privateFunc(){privateFunc();};
};
int main(int…
AudioDroid
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1
vote
0 answers
Friendship between two private, nested classes
I have 4 classes, A, A1, B, and B1. class A contains a private nested class A1, and class B contains a private nested class B1. I want the constructor for class B::B1 to have access to the private data members of objects of type A::A1. My solution…
mana
- 545
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1
vote
1 answer
Unable to use brace enclosed initializer-list while inheriting from friend class
I am trying to use an initializer list for a data structure which inherits from its parents friend class's subclass.
Below I compiled an example which demonstrates the problem(in c++11).
#include
#include
class i_gossip;
class…
Dávid Tóth
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