If i have a pointer array of classes, e.g. MyClass *foo; and if i try to delete this pointer delete [] foo; does it call a destructor of a class, or wahat happens? this is because i have another pointers in that class which are cleared in destructor.
View 1 RepliesIn this book, item 3 is about never treat arrays polymorphically. In the latter part of this item, the author talks about the result of deleting an array of derived class objects through a base class pointer is undefined. What does it mean? I have an example here,
Code:
class B
{
public:
B():_y(1){}
virtual ~B() {
cout<<"~B()"<<endl;
[Code] ....
This sample code does exactly what I want. So does the author mean the way I did is undefined?
I am trying to delete these arrays NumArray1.array and NumArray2.array at the end of my program so that there is not a memory leak. However I always get a double free or corruption error in runtime error with delete[] array_name. I have tried many times to use nullptr, but no matter what my compiler does not recognize it as being declared in the scope of my delete function. (I have commented out the that function for now.)
What is also strange about this is that I can perfectly use delete[] a1.array, which corresponds to NumArray1.array, but any of the other times I have tried to use the command, it has always resulted in syntax or runtime errors. Online resources do not adequately explain this scenario, though I am sure it exists elsewhere. all of my attempted solutions have failed, and I am completely at a loss. how to free the dynamically allocated arrays at the end of my program?
#include <iostream>
#include <assert.h>
using namespace std;
// Define a struct type, each struct type variable has three
// member variables: array, capacity, and length. Togther these
// three variable represent a partially filled array.
[code].....
LinkedList* listPtr = new LinkedList;
listPtr->addNode(3);
listPtr->addNode(4);
listPtr->addNode(6);
listPtr->print(std::cout);
delete listPtr;
listPtr->addNode(5);
listPtr->print(std::cout);
When I run the program it outputs
{ 3, 4, 6 }
{ 5 }
Why does the LinkedList object that listPtr is pointing to not get destroyed??
I create an instance of a base class (not derived class) and assign it to base class pointer. Then, I convert it to a pointer to a derived class and call methods on it.
why does it work, if there is a virtual table?
when will it fail?
// TestCastWin.cpp : Defines the entry point for the console application.//
#include "stdafx.h"
#include <iostream>
class B
{
public:
B(double x, double y) : x_(x), y_(y) {}
double x() const { return x_; }
[Code] ....
I am trying to delete a speific element in an array of class objects. i am overwriting the element i waant to delete with the element after it. My algorithm works but the output is not correct, after debugging it seems my objects just dont copy, is there a way to copy a class object, i have looked up copy constructors and attempted to write one but it does not seem to have any effect on the output.
below is my code
class user {
string firstname, lastname, currentteam, position, status ;
int age ;
public:
user() {};
[Code] .....
I am making a simple arkanoid game. When the ball hits the block, i want the block to disappear. How would i go around this? i am working in visual studio. I got the collision and everything working.. Here is my code;
int main(int argc, char** argv){
//initialisation
SDL_Init(SDL_INIT_EVERYTHING);
SDL_WM_SetCaption("Graphics Window",NULL); //set name of project
//variable declaration
SDL_Surface*screen;
boolrunning;
intgameState;
float startTime;
[Code] ....
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]....
I am confused whether 'malloc'ing an array of pointers and pointer to a group of arrays are the same.
Suppose I need an integer pointer to a group of arrays of 2 elements each.
int (*LR)[2];
So to dynamically allocate this pointer for M number of arrays suppose, then what is the correct syntax?
int M;
scanf("%d",&M);
int (*LR)[2];
LR = (int*)malloc(2*sizeof(int));
Whether this is correct??
The below example is an initialization of a pointer array:
char *month_name(int n) {
static char *name[] = {
"Illegal month",
"January", "February", "March",
"April", "May", "June",
"July", "August", "September",
"October", "November", "December"
};
return (n < 1 || n > 12) ? name[0] : name[n];
}
Here we have an array of character pointers. The pointers are stored in name[i]. And they point to the characters of the i-th string, which are stored somewhere else in memory. But Is the character pointer pointing to the first character in the character string that is stored somewhere else in memory? I assume so because a string itself is an array of characters. And if that is the case, how does the pointer know what the last character should be? Does it just search for the null terminator?
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);
}
My program is a basic MFC AppWizard (exe) created project in VC++ 6. In MainFrm.cpp, I am trying to access some user defined CMyView member functions. However when I try to do the standard procedure to get the CMyView pointer in MainFrm.cpp, I get the " ... 'CMyView' : undeclared identifier" error. To resolve this, I add " #include myView.h " at the top of MainFrm.h which then produces the following errors:
Code:
myview.h(21) : error C2143: syntax error : missing ';' before '*'
myview.h(21) : error C2501: 'CMyDoc' : missing storage-class or type specifiers
myview.h(21) : error C2501: 'GetDocument' : missing storage-class or type specifiers
What do these errors mean? Is there a simple way to access CMyView member functions from CMainFrame?
I'm trying to write a program to test if a string is palindromic using only pointers
Code:
#include <stdio.h>
#include <string.h>
void revstr(char* str)
}
[code]....
I need to change the arrays in the function int palin to pointers.
I have not been using pointers that long i most of my stuff has not needed them but now they do i need to learn how to use them more. I'm writing a program that simulates the squares most landed on(for fun) and i cant get a method to work because of an array pointer.
The error is no matching function for call to 'GameLoop::Loop(int, int (*)[4])'
Here is the latest version of the code. I've been editing a lot of things so there might be some stupid errors but I've tring everything.
rolling.h and rolling.cpp are just some dice function they are working perfect.
main.cpp
#include <iostream>
#include "Rolling.h"
#include "GameLoop.h"
Rolling Roll;
GameLoop Game;
[Code] ....
I'm trying to implement a class hierarchy and a wrapper class with a pointer to the base class. The base class has operator< overloaded and the implementation makes use of virtual functions as some of the logic for sorting is in the derived classes. Unfortunately, when trying to use the base class operator< from the wrapper, I get a "pure virtual method called".
Below code is meant to illustrate my problem. Unfortunately it crashes on me (upon destruction of vec) and I cannot quite see, why. So two questions:
1. spot the error I made in the code below (having lived in Java-land for the last 5 years, I'm sure I just did some stupid error)?
2. How can I implement Wrapper::operator< to use Base::operator<? I know I could write a function and pass it to sort but I'm interessted if there is a way to actually use Base::operator<.
Code:
#include <vector>
#include <algorithm>
#include <cmath>
[Code].....
I have encountered a problem I can't see to solve. I want to access a function and can't seem to find the right combination to get me there. Here is what I am looking at:
CFoo1::CFoo2::GetStrDataC(int nRow) const
How do I call the GetStrDataC function from another class?
I'd like to start out by adding an array to a C++ class. I'd like to be able to reference the array using a class object that I create, for example:
Class is Stone.
Stone Bob is an instance of "stone" that I name "Bob".
"Bob.array[1] = "granite";" tells the compiler that the second element in the array (with the first being the zeroth element) is a string containing "granite".
I'll eventually want to extend this to an n x m matrix within the "stone" class that can be referenced as: Bob.matrix[1][3]="lignite";
I tried to make this work using a text again and again last night to no avail. My code is below.
NOTE: Since I am dynamically allocating memory space, I'd like to avoid memory leaks when using this class with dynamically allocated arrays and matrices. Not sure how to do this. Also need some insight into "destructor", and why my simple version reduced to a comment below doesn't seem to please the compiler.
CODE FOLLOWS:
Code:
// AINOW.cpp : Defines the entry point for the console application.
//
#include "stdafx.h"
#include <iostream>
#include <string>
using std:: string;
using std:: cout;
using std:: endl;
using std:: cin;
[code]....
Class with Pointers and Dynamic Arrays
View 2 Replies View RelatedI have become overwhelmed an frustrated at these current operator overloads!
Currently I still can not get my +,* or istream operators working at all!
#include <iostream>
#include <cstring>
#include "myint.h"
[Code]....
I have a class which I need to initialize some arrays upon its creation. At first, I tried doing it like I would in Java -
float xyzw[4] = {0, 0, 0, 0}
but that didn't work. Then I had someone suggest using initialization list. I have done so below-
#include <vector>
#include "Buffer.hpp"
class Vertex {
public:
Vertex() :
xyzw{ 0, 0, 0, 0 },
rgba{ 0, 0, 0, 0 },
[Code]....
However, the above code gives me the following error:
Error1error C2536: 'Vertex::Vertex::xyzw' : cannot specify explicit initializer for arrays
I am using Visual Studio 2013.
Also, is there any way to edit previous posts? I keep making mistakes with the code tags.
In my case, it involves making a wrapper class of sorts for the std::set. I'm wanting to go all-out on it and make some "fashionable" constructors for it, one of which being similar to C-style array initializations.
// C-array initialization.
int array[5] = { 1, 2, 3, 4, 5 };
// Some example usage of what I'm wanting.
Set<long> num_set = { 10, 20, 30, 40, 50 };
Set<std::string> str_set = { "Hello", "I", "am", "a", "set." };
I almost never overload operators when I work--if it can be done with a function, it's done with a function--but I realize that doesn't make the best user-experience when other people come across your code, so that's what I'm trying to improve.
It looks like I'm going to be needing to overload the = operator, no big deal. But the array segment is confusing, since {} is not an overloadable operator in C++.
I am currently stuck on what I should do next in a program I am working on. These are my instructions:
Design, implement, and test a class for storing integer arrays "safely". The array should be able to hold any number of integers up to 100.
In the class header file "SafeArray.h" students must define the class and specify the constructor/destructor functions, the public methods and private variables. In the class implementation file "SafeArray.cpp" students must implement the following operations:
constructor - to initialize the object.
copy constructor - to copy an object.
destructor - to delete the object.
set - allow the user to set a value of the array at a particular location.
get - allow the user to get a value of the array at a particular location.
print - print out the array.
add - add the elements of one array to another.
subtract - subtract the elements of one array from another.
The output of my program is suppose to look like this:
Set q1: 2, 3, 4
Print q1: 2, 3, 4
Set q2: 1, 4, -2
Print q2: 1, 4, -2
Add q2 to q1
Print q1: 3, 7, 2
Get q1 at 1: 7
Here is the code I have so far.
*main.cpp*
#include <iostream>
#include "SafeArray.h"
using namespace std;
int main() {
// Declare a SafeArray object
Safe obj;
[Code] ....
I'm having trouble with passing a character array between functions of the same class. I have a function, buildGraph, that calls function getNextLine. The getNextLine essentially just retrieves the next line of an input file and stores it into a "char line[80]". However when I try to use "line" in my buildGraph function, it has nothing in it.
Here's my code:
Class
#define NUMNODES 10
using namespace std;
#pragma once
class Prog3Graph
[Code] ....
I'm currently reading the C++ Guide for Dummies
Anyway right now I'm working with pointers and classes, and when I create a new pointer for my class it looks like this...
Pen *Pointerpen = new Pen;
But in the book they threw in this...
Pen *Pointerpen = new Pen();
Can you actually designate memory space for a function? Or was this a typo on their part? It's never come up before and they didn't explain it.
A pointer to base class, if assigned to a derived class, only points to the base part right? So you can only use the base part of the derived class with that pointer and no methods from the derived class?
View 8 Replies View RelatedI came across a piece of c++ code that seems to be initializing a class object like this:
ImapMailbox *mailbox;
Now the class looks like this:
class ImapMailbox {
public:
ImapMailbox();
ImapMailbox (const QString& mailbox);
~ImapMailbox();
// Methods
void addMessage (ImapMessage *message);
[Code]...
And the constructor looks like this:
ImapMailbox::ImapMailbox()
: d(new ImapMailboxPrivate)
{
d->unseen = d->exists = d->recent = 0;
d->readWrite = false;
d->flags = 0;
}
But this does not seem to be an array like object. So what exactly could this be pointing to?