C++ :: Create Assignment Operator For A Class That Uses Pointer For Its Private Variable?
Mar 30, 2013
i am trying to create the assignment operator for a class that uses a pointer for it's private variable. The error is saying expected constructor, deconstructor, or type conversion before "operator. (which is the assignment operator. I have tried everything i could think of or find online and nothing has worked. below is the code for the assignment operator in the .h file and the .cpp file.
//Assignment constructor
indexList &operator=(const indexList <T> &rhs);
template <class T>
indexList<T>::indexList operator=(const indexList <T> &rhs) {
if(this != &rhs) {
numberOfElements = rhs.numberOfElements;
[Code]...
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Mar 6, 2014
Class A
{..........}
Class B:
{....
private U& u;}
I need to write the copy constructor and assignment operator for Class B above. Copy would look something like this:
B::B(conts B& bo): u(bo.u){}
is this correct ... and how will the assignment operation look like??
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May 23, 2013
I designed a class template to create unique arrays. I was able to successfully input data to and output data from my array objects, irrespective of the datatype. However, I can't for the life of me fathom why my overloaded assignment operator worked perfectly well only for integer datatype and not for double/string datatypes.
Here is the class definition:
template <class dataType>
class myArray {
public:
void setArrayData();
[code]....
And here is the definition of the overloaded assignment operator:
template<class dataType>
const myArray<dataType>& myArray<dataType>::operator=(const myArray<dataType>& rightArray) {
int i;
if(this != &rightArray) {
delete [] arrayPtr;
[Code] ....
And here is my main function that tests the operations on objects of the class:
int main(){
//object declarations
myArray<double> list(5); //a single-parameter object declaration of class myArray
myArray<double> myList(2,13); //a two-parameter object declaration of class myArray
[code]....
The problem I'm having starts from where the assignment operator is being tested: for double and string datatypes, the upper input/output section works fine, but the assignment section freezes the display until the program execution is manually terminated!
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Sep 30, 2014
I want to make a destructor counter...So it needs to be outside that specific instance of the class. And i want to keep it hidden. I don't want to be able to access it from outside the class...I Don't want main.cpp to have access to this variable
Is there a way to do this?
static int destructorCount;
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Oct 23, 2014
The question is: Define the class Counter. An instance of this class is used to count things, but the counter should never be less than 0 (non negative number). The member variable should be private. I realize what I'm suppose to be using but can't implement the member functions needed..
int main(){
int value;
cin >> value;
Counter myCounter(value);
for (int i = 1; i <= MAXLOOP; i++) {
myCounter.increment();
[Code] ....
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Mar 6, 2013
Below is a working program. Please note that the vector <int*> pointer is declared as a public member of the class A.
The problem arises when I try to make it a private (instead of public). First, let's look at the File 1 below. It compiles and works fine.
File 1: main.cpp (working fine)
#include <vector>
#include <iostream>
using namespace std;
[Code].....
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Feb 1, 2015
I have code here that uses assignment operators that doesn't return by reference and it still works. So why does my book say you need to return by reference?
Here is a quote from my book:
The return type of operator= is a reference to the invoking object, so as to allow chained
assignments a=b=c.
The code below is from my book. I simply removed '&', in the original code that has assignment operators return by reference, from IntCell & operator=. This way the assignment operator no longer returns a reference, and it still works.
#include <iostream>
using namespace std;
class IntCell {
public:
explicit IntCell( int initialValue = 0 )
{ storedValue = new int{ initialValue }; }
[Code] .....
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Apr 7, 2014
I am wondering why return type for an assignment operator cant be a void or int? Cant I write assignment operator for student class like this as we do nothing with returned value?
Student {
char name[20];
int marks;
public:
student(char*name,int marks)
[code].....
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Jan 9, 2015
The task is to use the assignment operator of a class, but change all the data except certain ones. For example, below we are to assign all Person data of 'other' except for 'name' and 'ID':
#include <iostream>
#include <string>
struct Person {
std::string name;
int ID, age, height, weight;
[Code] .....
Name = Bob
ID = 2047
Age = 38
Height = 183
Weight = 170
Name = Frank
ID = 5025
Age = 25
Height = 190
Weight = 205
Bob pretends to be Frank, but keeps his name and ID.
Name = Bob
ID = 2047
Age = 25
Height = 190
Weight = 205
But I think the way I did it is pretty lousy (note the wasted steps changing the name and ID only to revert them back? So the ideal solution should require no wasted steps, unlike the method above, and changes to what the exclusions should be should be in only one place (not two like above). Of course, we assume that Person shall have many, many data members (and constantly increasing), so that simply defining Person::operator= (const Person& other) to handle all data except for 'name' and 'ID' is out of the question.
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Feb 3, 2014
How do i write main test program to test the copy constructor and assignment operator in this program...how do i know if its working as its suppose to?i just want to know about copy and assignment operator..i have figured out the test program for other things..Here my program :
ListType.h
#ifndef LISTTYPE_H
#define LISTTYPE_H
#include<iostream>
class ListType{
public:
ListType(size_t=10);
ListType(const ListType&);
[Code] ......
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May 20, 2013
I've been working on some project and I got to wondering when you know you need to use a copy constructor and an assignment operator. Is there a rule of thumb? I know there is the Rule of Three, but is there something that tells you when you need those three?
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Apr 11, 2014
Below is exception proof approach of assignment operator shared by scott meyer. Is it safe to delete the raw pointer.
int *orig =m_p;
m_p=new int (*obj.m_p);
delete orig;
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Sep 13, 2013
Go to this link : [URL] .....
Actually I am not getting one thing in this code that why they only provide the declaration of Copy constructor and Assignment operator...??
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Nov 12, 2014
how the operator overloaded methods called in C++?
Class String {
int len;
char *str;
public:
String(const char *str1="") {
len=strlen(str1);
str=new char[len+1];
strncpy(str,str1,len+1);
[code]....
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Jul 27, 2012
/*using GENERIC_COMMAND* A; as volatile generates error. but here i have to use union object as volatile i.e. volatile GENERIC_COMMAND* A; */
#include <iostream>
using namespace std;
typedef unsigned int uint32_t;
typedef unsigned long long uint64_t;
union GENERIC_COMMAND {
[Code] .....
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Nov 29, 2014
I have a class called Book and I am trying to create a dynamic pointer based array of the class. When I try to run the program I keep getting the error: pointer being freed was not allocated at the line of code that says "delete [] A;". I am using Xcode to run the program.
Book *changeArraySize(Book *A, int &size, double factor) {
int i;
int newsize = size*factor;
Book *A2 = new Book[newsize];
[Code] ....
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Dec 1, 2013
How can I add the variable adress to a void pointer inside of a class?
class variant2 {
private:
void *Vvariant=NULL;
public:
template<typename b>
variant & operator = (b *adress)
[Code] ....
if possible i want avoid the '&' when i assign the variable address.(variant2 f=varname;//like you see i don't use the '&')
for the moment i just need put the address to Variant pointer. but i receive several errors .
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Jul 27, 2013
when i compile the following program i get a compiler warning, but i don't understand why. for me the code seems to be all right and does legitimate this warning. so here is the code
// multiplication.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include "crypto.h"
#define PROGNAME "multiplication"
void usage();
int isnumaber(char* str);
[code]....
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May 15, 2013
I have a class with member functions and a pointer like this:
Code:
class MyClass{
private:
typedef void(MyClass::*memFnPtr_t) ();
public:
memFnPtr_t fnptr;
void fn1();
void fn2();
};
Now in a regular function I create an instance of the class and try to assign the pointer:
Code:
MyClass mc;
mc.fnptr = &mc.fn1;
The compiler does not like it and suggests this instead:
Code:
mc.fnptr = &MyClass::fn1;
This seems to work but what if I have two instances of the class:
Code:
MyClass mc1, mc2;
How does the compiler know to distinguish between
Code:
mc1.fn1
and
Code:
mc2.fn1
when the assignment now looks identical:
Code:
mc1.fnptr = &MyClass::fn1;
mc2.fnptr = &MyClass::fn1;
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Apr 17, 2014
I'm working on a program and everything works except for the follow function:
void swapHex(int x, int byte1, int byte2) {
unsigned char *b1, *b2, tmpc;
printf("%d in hex is %x
", x, x);
printf("swapping byte %d with byte %d
", byte1, byte2);
[Code] ....
I get the following errors when compiling:
In function "swapHex":
warning: assignment from incompatible pointer type
warning: assignment from incompatible pointer type
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Jul 4, 2013
The log file gives me: In function ‘memFileAlloc’ assignment makes pointer from integer without a cast..When compiling the drivers for the Matrox card in the DL580. The offending code is:
STACK_LINKAGE MEMHANDLE memFileAlloc(
UINT32 dwSize,
const char* pszFileName,
int iLine) {
void* pvChunk;
#if MEMORY_STATS
[code]...
I think the offending line is:
pvChunk = ClientMemAlloc(dwSize + sizeof(UINT32), NULL)
because that's what the log file tells me.
The system is a 16 core HP DL580 G4 with 8g RAM, RAID 0, Mandrivalinux 11.0 and the display is a Matrox Parhelia 256PCIx.
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Nov 6, 2014
How can you actually create private fields in a C struct? I got the concept of VTable and inheriting methods aswell overriding them, but private variables can be obtained with static keyword in sourcefile. If you have variables in a struct, you can access them as soon as you got a ref to the struct. The functions are easy:
Code:
struct classA {
pointerToFunction *p;
} static void* thePrivateFoo() { }
void* publicFoo() {
thePrivateFoo(); /* or something like that */
} ...
/*in init code somewhere in the c file */ classAInstance->p = publicFoo;
But I was thinking about the variables... How is this achievable? I was thinking of a struct with only get/set functions and with no datamembers at all. All vars to be static outside the struct. But this kind of destroys the encapsulation.
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Nov 8, 2014
So I'm doing this project: [URL] ....
For now I've done a function that creates menus and prints them, and a function that creates the character as an object.
Now I want to be able to show the stats of the player on the main menu, the problem is that I don't know how to make a copy of the map as it's private...
Main
#include <iostream>
#include <string>
#include <time.h>
#include <stdlib.h>
#include <map>
#include <algorithm>
#include <stdlib.h>
#include "Create_Character.h"
#include "Menu.h"
[Code] ....
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Apr 3, 2013
I've created a class called Voter with a private member variable ID, also I have a variable in my main function to be ID as well. I'm trying to compare the two ID's but when I do so:
if (ID == V.ID)
I get the error - 'std::string Voter::ID' is private within this context.
I know that because it's private I can't access it, but how do I?
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Jul 10, 2014
I have a this program of storing students in a 2-3-4 tree. I have a template class called hw6_234tree and another class called Student. Now my private member variable (m_root) keeps being reinitialized every time I process a new line. For example the first student I run through my m_root->A = Student A...(m_root is a private variable of type Node* inside of the 2-3-4tree class).The next pass through now my m_root->A == Student B. So essentially my first run through m_root->A = Student A. Then the next run m_root->A = Student B. My question is how can I keep this variable the same and stop it from reinitializing m_root->A to student B.
Here are a few snips of the code:
Function in main:
void ProcessLine(string line, hw6_234tree<Student>& tree)
Function call:
tree.Add(Student(id, name));
Private Variable:
Node* m_root;
A function for a struct named (Node) in the private section of class hw6_234tree that assigns variables in the struct to values:
Node(T* valueForA)
{
A = valueForA;
B = C = NULL;
L = M1 = M2 = R = NULL;
}
The start of my Add function:
bool Add(T& toCopyAndAdd)
{
if (m_root == NULL)
{
m_root = new Node(&toCopyAndAdd);
return true;
}
return false;
}
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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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