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]....
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] ......
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?
View 4 Replies View RelatedGo 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...??
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] .....
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].....
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.
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;
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??
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!
/*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] .....
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]...
Allow users to enter their name and favorite saying in a single method that gets invoked two times. If I can only return one value at a time, how am I suppose to get name and favorite saying out of UserInput()?
static void Main(string[] args) {
string displayName, favoriteSaying;
DisplayInstructions();
Console.WriteLine();//readability
[Code] ....
Im trying to create a map container with the key being an ID number and the value being a pointer to a class object. Currently Im creating objects and storing their address in the container. I am getting a runtime error when calling the virtual method with this pointer. I believe that the problem is being called because they aren't being called pointer/reference. let me know if you need more.
if(command == 'F'){
inputDataFile>>name>>mNumber>>email>>department>>tenure;
faculty newFaculty(name,mNumber,email,department,tenure);
person* facultyAdd = &newFaculty;
cout<<"Note: Adding "<<mNumber<<"..."<<endl<<"Adding ";
people.insert(pair<string,person*>(mNumber,facultyAdd));
[Code]...
I am trying to write a method (copyStack())that copies the elements of one stack to another. So I am using a Type variable and a while loop, assigning the top of the first stack to the variable, and then using the push method to push the Type variable into my second stack (then poping the first stack). However, whenever it comes time to print the second stack (the one I am trying to copy into), nothing shows up. I know that the program is reaching the copyStack function, and I know that when I put a regular string in for the Type variable, it passes that string along. But for some reason, when I use the variable, nothing happens! Here's what I've got...
header file containing stack manipulators:
//Header File: linkedStack.h
#ifndef H_StackType
#define H_StackType
#include <iostream>
#include <cassert>
using namespace std;
[Code] ....
I'm still working on my process API, as in my previous posts. Right now I'm trying get my class portable so I can use it for any language/compiler by using a factory design pattern. I'm having problems figuring out how to call the methods properly from my interface pointer in my factory class without causing a segmentation fault.
Code: main.cpp
Code: #include "exports.h"
#include <iostream>
using namespace std;
[Code]......
I would like to avoid throwing things in constructors as much as possible.
Is this good design to have a static class method that checks arguments the caller will give to the constructor. The documentation of the class will say, thou shall call this method to validate thine arguments before calling the constructor, or else segfault may befall thoust.
I have a COM Object created using ATL (without MFC Support)
The Object has 1 method that opens a Dialog (that does all the rest) and when finish - returns 2 values back (1 is enough)
Currently I call it from another EXE:
hr = CoCreateInstance(
CLSID_MyControl,
NULL,
CLSCTX_INPROC_SERVER,
IID_IMyControl,
(void**) &pMyControl
);
and then:
hr = pMyControl->MyMethod (ATL::CComBSTR(InputString1), ATL::CComBSTR(InputString2), &IntReturned, &IntReturned);
Is it possible to call it as is from a browser ?
How can I Instantiate the object and invoke my method (with params) from the browser ?
will it open the dialog ?
class IFoo {
virtual void Bar() = 0;
};
class FooAbstract {
virtual void Bar() {}
[Code] .....
How to call the Bar() method from FooTemplate in FooDerived::Bar()?
I'm working on a project and I'm not quite sure how to implement the Copy constructor and Overloaded assignment operator.
This is what the instructions say if that matters at all: Since you have dynamic variables in your class, you should make sure that the big three are implements. You already have the destructor, but you will need to add a copy constructor and the overloaded assignment operator. This is simpler than it sounds, but it requires some thinking. You need to make sure that both the copy constructor and the assignment operator create new containers.
Here is my header file:
#ifndef CANDIDATELIST_H
#define CANDIDATELIST_H
#include "CandidateType.h"
#include <iostream>
[Code].....
I know I don't have much in these functions but I'm not sure how to apply them or if I'm even headed in the right direction.
In main I instantiate two Polynomial objects -- p1 and p2:
int main() {
const int SIZE = 3;
Polynomial *p1 = new Polynomial(SIZE);
Polynomial *p2 = new Polynomial(SIZE);
//Read data into p1
std::cout << "Initialize Polynomial Coefficients (1)" << std::endl;
[Code] .....
The implementation file for Polynomial is as follows:
Polynomial::~Polynomial() {
delete [] this->m_Ptr;
this->m_Ptr = NULL;
} Polynomial::Polynomial(int size) {
[Code] .....
What works: Adding two pointers. The output is correctly produced.
The problem in particular occurs in main when p1 and p2 are attempted to be multiplied. The code attempts to release the memory upon multiplication but I receive a run-time error.
The output for the difference of the two polynomial objects is incorrect. It is displaying addresses.
I have a program which when a button is clicked on Form1 it runs a vision system operation on an image in a window on a Form1. There are also other buttons on the Form1 which can change things like threshold levels so the inspection can be run again with different settings. It all works fine but I want to change it to remove the buttons from Form1 so that when the user clicks on a button on Form1 it opens up another form, Form2, and all the buttons which were on Form1 are now on Form2 and the image analysis should run on Form1 when the buttons are used on Form2. I have taken over all the code from Form1 to Form2 and I'm trying to make this happen by creating a new oject on Form1 which calls a method on Form2 which contains the code which was in Form1 and called when the button was clicked on Form1 - not working!! I have a constructor in Form2 but I think I have become monumentally confused.
This was the code which was on Form1 when the inspection button was clicked.
private void cmdInspectOnce_Click(object sender, EventArgs e)
{
iReturn = VisionSystem.InvModeSet(IpeEngCtrlLib.I_MODE.I_EXE_MODE_ONCE);
if (_imgEngines!=null && _imgEngines[0]!=null)
_imgEngines[0].cmdInspectOnce();//InvModeSet(IpeEngCtrlLib.I_MODE.I_EXE_MODE_ONCE);
}
I've been trying for more than one month to access a method found in a library called libcocosnas_static.a. I'm using Cocos2d-X version 2.0.4. The library has been used many times by my company to make games using cocos2d-1.0.1-x-0.12.0 without any problem.
This is what I've done:
1- I added the include paths of the library to both eclipse and Android.mk
2- Included the .h file using #include "NASPlatformUtil.h"
3- Added the libcocosnas_static.a file to the proj.androidobjlocalarmeabi folder
4- Added "LOCAL_WHOLE_STATIC_LIBRARIES += cocosnas_static" to the Android.mk file
5- Called the function using: NASPlatformUtil:: openUrl("http://xxx.xxx.com/");
I can right click on the function, click Open Declaration and get it without any problem, but the compiler keeps on giving me that dreaded error...
I'm doing a refresher for C++ and have gotten to operator overloading. I'm trying to perform an operator overload with the insertion (<<) operator, but I have encountered a problem.
Here's my class [In a header file "Shinigami.h"]
#include<string>
namespace K{
class Quincy;
class Shinigami{
friend std::ostream& operator<<(std::ostream&, const Shinigami&);
[Code] .....
If the operator function is a friend of the 'Shinigami' class, why doesn't it recognize any of it's private members? I need it to be in this file because I'm doing a bit of association with the 'Quincy' class.
I thought it was the namespace, but I included that.
I have a question similar to the one here: [URL] .....
The main difference is I would like to pass a method of derived class as a parameter to some other method in its template base class.
template <typename BaseType>
class Base {
public:
typedef void (Base::*Callback)(int A);
[Code] .....
The above is an example which does not compile. My compiler complains that the two BaseMethod() calls in DerivedMethod() are invalid uses of non-static member function.
Is this not possible to do, or is my syntax simply wrong? All I want is to be able to pass as an an argument to a method in the base class from the derived class some callback as a variable for the base class to invoke later.
I am using OpenCV to read and manipulate a set of images, which I need to store in an array to work with them. Here is a snippet of the code:
#define MAX_IMAGES 8
typedef Mat* MatPtr;
int main(int argc, char** argv) {
char imageName[] = "./res/imageX.tiff";
MatPtr datacube[MAX_IMAGES];
[code].....
I have an array of pointers to Mat objects (an OpenCV class used to hold info and data about an image), which I will use to store the images. The function imread reads an image and returns a Mat object loaded with the relevant data about the image.However, this gives me a nice segfault when the assignment takes place. Of course, I can swap it with the following code, but since I'm working with big images (2048x2048 and upwards), it's really inefficient:
for(unsigned int i = 0; i < MAX_IMAGES; i++) {
imageName[11] = 49 + i;
datacube[i] = new Mat(imread(imageName, -1));
}
Is there any way to do this elegantly and without much hassle?Again, excuse my rustiness and anything completely stupid I might have said. It's been a long time since I worked with C++. Managed to circumvent the problem by using a STD vector instead of an array. I'd still like to know the answer to this riddle...