C++ :: Constructor That Initializes A Pointer To Point To The Object
Aug 27, 2013
I have a program that has a base class 'control' and there are 2 dervied classes 'button' and 'textbox'. How do i make a constructor in the 'button' or 'textbox' that initializes a pointer of the data type 'control' to point to the object that invokes the constructor. the code should look like this
class control {
//data
} class button:public control {
buton() {
//code for the constructor
}
}
actually i have an array of pointers of the type 'control' and as soon as any instance of a control like button or textbox is created the constructor should make an element of the array to point to the instance
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Feb 23, 2014
Write a constructor that initializes a new inventory object with the values passed as arguments, but which also includes a reasonable default value for each parameter.
#include "stdafx.h"
#include <iostream.h>
#include <stdio.h>
#include <string.h>
class inventory {
[Code] ....
I am not trying to get my homewotk done, just to understand my errors. It complies without problem. But doesn't run.
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Mar 16, 2013
will copy constructor does object initialization using another already created object? I understand that it can be applied for object initialization and not for assignment.Is it correct?
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Jan 25, 2014
VS 2012 / Windows 7 64 bit
class
class myclass {
public:
myclass(){/*stuff here*/}
myclass(int* p) {MyPointer = p; myclass()}
[Code] ....
it works until the myclass(int* p) calls myclass()
then the MyPointer will become CCCCCCCC (NULL value)!
is there a way to stop the second constructor from resetting the pointer value to null?
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Mar 28, 2014
I am trying to use web api in order to return custom json response keys. For this i have return a custom class to return json response
Custom Class:
using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
[Code].....
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Mar 11, 2013
is it possible to get object name in the constructor? I would like to initialize an object of circle class without any arguments and put some pretty lines in constructor to get and save as table of chars the name of creating object. Is it possible? I work with MSVS2012.
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Aug 19, 2014
I am attempting to implement function pointers and I am having a bit of a problem.
See the code example below; what I want to be able to do is call a function pointer from another pointer.
I'll admit that I may not be explaining this 100% correct but I am trying to implement the code inside the main function below.
class MainObject;
class SecondaryObject;
class SecondaryObject {
public:
[Code]....
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Oct 15, 2013
sth is in my mind.
fast way of initializing an object through constructor is
Fred::Fred() : x_(whatever) { }
slow way
Fred::Fred() { x_ = whatever; }
ok. i accept it is faster but why?? what is the difference compiler does.
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Jun 24, 2013
I have a question about the default constructor.
To my best understanding, the compiler will provide me with a deafult constructor only if there are no any user defined constructors, at all. Now consider the following code:
Code: class MyClass
{
private:
int m_data;
public:
MyClass(int init):m_data(init){cout<<"Ctr called"<<endl;}
[Code] ....
How is it that suddenly, there is a default constructor?
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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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Jan 31, 2013
Do I really need to create a separate pointer to point to dynamic arrays?
T* temp = new T[capacity_ * 2];
T* tIter = &temp; //Do these need to be here?
T* dIter = &data; //Or can I use *(temp + i) and *(data + i)?
(for unsigned int i = 0; i < size_; i++) {
*(tIter + i) = *(dIter + i);
}
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Jul 5, 2013
I am creating a Matrix class, and one of the constructors parses a string into a matrix. However, printing the result of the constructor (this->Print()) prints what I expect, and an <object_just_created>.Print() call returns bogus data. How is this even possible?
Snippets below:
Matrix::Matrix(const string &str) {
// Parse a new matrix from the given string
Matrix r = Matrix::Parse(str);
nRows= r.nRows;
nCols= r.nCols;
[Code] ....
in the driver program, here are the two successive calls
Matrix mm6("[1 2 3.8 4 5; 6 7 8 9 10; 20.4 68.2 1341.2 -15135 -80.9999]");
mm6.Print();
// mm6.Print() calls bogus data, -2.65698e+303 at each location. The matrix's
// underlying array is valid, because printing the addresses yields a block
// of memory 8 bits apart for each location
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Mar 24, 2014
This keeps giving me the error
ecg.h:18:11: error: field "next" has incomplete type
How do I do what I need? It does the same thing whether I use a class or a struct. This is C++ code
struct ECG_node {
double voltage;
clock_t time;
ECG_node next;
[Code] .....
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Jan 30, 2013
I'm trying to pass an reference of the object ifstream to my constructor as such:
// myClass.cpp
int main(){
ifstream file;
myClass classobj = myClass(file);}
I am defining the constructor as follows, in myClass.cpp:
myClass::myClass(ifstream &file){
// do stuff
}
I get the error of "No overloaded function of myClass::myClass matches the specified type."
Also, when I build the program, it tells me "syntax error: identifier 'ifstream'"
Also, I made sure I included this:
#include <iostream>
#include <fstream>
#include <sstream>
What am I doing wrong? How can I pass an ifstream reference to my constructor?
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May 9, 2013
I've got a struct called Node that contains, among other things, a pointer to a vector of pgm objects. (pgm is a class i've created)
struct Node {
int label;
vector <pgm> *ptr;
Node* lessNode;
Node* moreNode;
};
in another class, i create a vector and a Node and am having trouble assigning the pointer in the Node to point to my new vector.
vector <pgm> lessData;
Node* left;
left->ptr=&lessData;
This all compiles ok, but the last line in the code above causes a segmentation fault. I should mention Node is declared on its own in Node.h and what pgm is. including pgm.h in node.
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Nov 24, 2014
I want to copy over values from x to y, and its not possible as i cant use "y" as a index in my pointer array.
Code:
CellularPhoneStock::CellularPhoneStock(CellularPhoneStock &origObj){
this->phonez[nrOfPhones]->setColour = origObj.getColour();
/*this->model = origObj.model;
this->nrOfType = origObj.nrOfType;
this->price = origObj.price;*/
nrOfPhones++;
}
My questions is, how can I use origObj and phonez combined to use the function getColour() ?
Btw, phones = CellularPhone * phonez[30];
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Jan 30, 2014
Is this the correct format to point a pointer (pointer1) to another pointer (pointer2)?
&pointer1 = &pointer2
I am kinda rusty when it comes to pointers ...
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Feb 20, 2012
class Base
{
char * ptr;
public:
Base(){}
Base(char * str)
[code].....
Obj1 is a derived class object where base class char pointer is initialized with "singh" and derived class char pointer is initilized with "sunil". I want to create Obj2 out of Obj1. Separate memory should be created for Obj2 char pointer (base part and derived part as well) and that should be initialized with the strings contained in Obj1.
Here the problem is: Derived class part can be initialized with copy constructor. How to initialize the base class char poniter of Obj2 with the base class part of Obj1. char pointers in
both the classes are private.
I tried using initializer list but could not succeed.
Is there some proper way to do this?
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Feb 19, 2013
I know my product.cpp constructor is wrong but how can I set my private variables.
//PRODUCT.h
#ifndef PROJECT1_PRODUCT_H
#define PROJECT1_PRODUCT_H
[Code].....
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Dec 3, 2013
I have little problem which causing memory leaks.
Parent > Multiple Child(Parent parent) > Child destructor deleting parent => next Child destructor crash
Example code: without using:
class Parent {
public:
Parent() {
for(int i = 0; i < x; ++i) {
for(int j = 0; j < y; ++j)
childs[i][j] = new Child(this);
[Code] ....
If you read code, on Parent destructor i = 0 & j = 1 its going crash.
Parent will be deleted aswell, but it give me assert: _block_type_is_valid(phead- nblockuse)
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May 24, 2012
I am migrating a scientific code from Java to C++.
What's wrong with the two functions? I can use the int** like a two dimensional array but not the Agent**.
I receive this error: "No operator = matches this operand".
(I have allocated two dimensional arrays for objectSpace and agentSpace somewhere else).
Code:
int** objectSpace;
Agent** agentSpace;
void Space::removeAgentAt(Point p) {
agentSpace[p.x][p.y] = NULL;
}
void Space::putAgentTo(Agent agent, Point newP) {
agentSpace[newP.x][newP.y] = agent;
}
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Apr 12, 2013
i need to pass myboard.board (board is in the class Cboard and it is an array of int) to a function in a class called piece however this is troubling . i need to pass it as pointer os that i could change its value here under is my code.
main.cpp Code: #include<iostream>
#include"board.h"
#include "pieces.h"
[Code].....
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Aug 4, 2013
#include <iostream>
#include <vector>
#include <string>
#include <map>
using namespace std;
struct bop {
string realname; //real name
[Code] ....
Okay, so first thing's first. The program will not compile due to lines 39-45. If I were to change those pointers into regular objects, it will not change the values of my class object. So what is the right way to do this?
I want the user to be able to input the # of employers/programmers into the system. But I cannot do that with an array of classes because when declaring an array; the array size must be constant.
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Jul 23, 2013
I have pointer object and i have to assign to another variable ( new object ). But if i change any value in new object should not reflect in old object. I did in the below way, it changes the value.
class Test {
public:
int num;
};
Test* obj;
obj.num=1;
Test obj_n=*obj;
obj_n.num=2;
Now both object's num have value as 2;
i.e
obj.num // has 2
obj_n.num // has 2
Actually my expected result is:
obj.num - should have value 1
obj_n.num - should have value 2
My actual scenario is different where Test obj is pointer object, so obj should be pointer object. i have given sample scenario.
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Aug 16, 2013
I have the following code.
StackElement *StackElementArray;
StackElementArray = new StackElement[iMaximumDepth];
I want to assign one element of this array StackElementArray the address of another object. For example,
voidStackMem::push(StackElement &iStackElement) {
CurrentDepth++;
StackElementArray[0] = iStackElement;
}
The StackElement class contains pointers to some dynamic arrays. When I use the assignment, StackElementArray[0] = iStackElement;, it doesn't copy the complete contents and I have to define an 'assignment operator' function to copy all the contents. I am wondering if there is a way I can assign StackElementArray[0] the pointer to the StackElement object. In that case, I will not need to copy the contents of iStackElement into StackElementArray[0] and will just copy the address.
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May 30, 2013
I'm making a code that uses a Function pointer. The problem is, when I try to compile appears an error like:
error: no matching function for call to 'rnVector::rnVector()'
Here's part of the code:
phiFunction::phiFunction(double (*f)(rnVector), rnVector (*df)(rnVector)) {
//... Here comes the code stuff...
}
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