C++ :: Creating Objects Dynamically?
Nov 11, 2013
How would I implement a way that i could create as many objects as the user wants?
Let's say every time a user clicks space bar a new cat object would be created, because right now i create lots of objects without initializing and every time i get a input i assign values to the object, the downside is that is limited for the amount of objects i create.
As well i don't want to cause a memory leak, specially in c++ because i need to use the delete keyword.
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Jul 26, 2012
Project compile successfully but console turn off with "Windows " with error doesn't print or get anything
Code:
#ifndef Point_HPP // anti multiply including gates
#define Point_HPP
#include <string>
#include <iostream>
#include <sstream>
#include <cmath>
[Code] .....
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Jan 16, 2013
Please consider the following code :
#include <iostream>
using namespace std;
class superclass;
class subclass1;
class subclass2;
[Code] ....
As you can see I want to create a dynamically allocated storage of references to a parent class each of which can then point to a child class, how ever I do not know how to extract the child class out again from that array so i may access its variable b.
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Nov 3, 2013
regarding dynamic vector.
Shape2DLink.cpp
void Shape2DLink::InputSensor()
{
string shape,type;
[Code]....
So i'm actually using polyphormism for calculating the area of the cross and other shapes. so how do I actually make use of dynamically create an object this way?
do I create them in my Shape2DLink or in my individual child classes?
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Apr 6, 2014
I have a structure, containing a pointer as a member. I dynamically create an array of that structure type, and then need to dynamically create an array for its pointer member.
#include <iostream>
#include <string>
using namespace std;
[Code]....
There is more of my program afterwards, but it shouldn't matter. The errors I am getting at compile time are that I cannot convert an int pointer to an int (line 29) and that test is not a member of CourseGrade (lines 44/45).
My thought is I might be using the * operator incorrectly. My code before hand in line 29 was
for (i = 0; i < numberStudents; i++)
*studentPtr[i]->tests = new int[numberTests];
but the compiler suggested a '.' rather then the '->'
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Dec 16, 2012
I'm using CStatic inherited class in my code and creating static text boxes dynamically. Now for assigning unique control ID I'm creating a static control from resource editor and destroying it before calling CStatic::Create() and using its control ID say ID_STATIC_SAMPLE.
If I do not use this parameter of Create(), the static control is also being created, so what is the use of this unique ID. And any other better way to assign a ID for dynamically created static controls.
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Nov 4, 2013
Im supposed to create an to array of eight Circle objects initialized with the following radii: 2.5, 4.0, 1.0, 3.0, 6.0, 5.5, 3.5, 2.0. Then use a bubble sort to arrange the objects in ascending order of radius size before displaying the area of each object.
The error I get is "Cannot open include file: 'Circle.h': No such file or directory". Do I have to create a separate file for it?
#include <iostream>
#include <iomanip>
#include "Circle.h"
using namespace std;
class Circle {
public:
Circle()
[Code] ...
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Oct 21, 2014
I'm working on designing a game in C++ that is similar to the "find the ball under the cup" game. I have a Sonic the Hedgehog icon (weird I know, but it was the first thing that came to mind) that will be hidden underneath one of three rectangular blocks.
Here is how I envision this working:
On the main menu I have 3 buttons which represent 3 different difficulty levels
Easy- blocks move 3 times at a slow speed
Medium- blocks move 5 times at a slightly faster speed
Hard- blocks move 10 times at a fast speed
When the user clicks one of these buttons they will be taken to the game screen.
Sonic will be displayed for 3 seconds and the user will then see him be covered with one of the three blocks.
The three blocks will then move in a random pattern along the middle of the screen at the speed and number of times associated with the button that was pressed.
Once the blocks stop moving, the user is to click on the one they think Sonic is underneath.
If they choose correctly, they'll be taken to a "Winning Screen" that displays a congratulatory message and 2 buttons. Play Again- returns the user to the main menu and the game starts over with a new random pattern. Quit- the window closes.
If they choose incorrectly, they'll be taken to a "Losing Screen" that displays a "Try Again" message and 2 buttons that have the same function as the buttons on the winning screen.
I have never worked with any kind of graphics before other than in HTML and Javascript. I have managed to create the main menu, but how to do the actual game portion of the project. I've been trying to take it a step at a time, (for example, I first figured out how to set the background color for the console window, after I got that right I figured out how to add buttons) but the rest of this seems to depend on each other.
Here is what I have so far:
Main menu:
#include "stdafx.h"
#include <iostream>
#include <Windows.h>
using namespace std;
class MainMenu
[Code]....
So I've got the screens pretty much designed now (with the exception of the game screen itself) but how to tie everything together.
In case my description wasn't too clear, here is a game that I found on Google that is pretty much exactly what I'm looking for. [URL]
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Mar 16, 2014
I am creating a game and I using classes for other things in my game, I was wondering if i should use classes for rendering objects?
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Dec 4, 2013
I've got 2 classes, Store and Transaction and I would like to create a priority queue of objects Transaction as a variable of Store class.
My store.h
#ifndef __STORE_H_INCLUDED__
#define __STORE_H_INCLUDED__
#include <queue>
using namespace std;
#include "Transaction.h"
struct TransactionCompare;
[Code] ....
The error im getting with this set up is
error C2664: 'bool TransactionCompare::operator ()(const Transaction &,const Transaction &)
const' : cannot convert parameter 1 from 'Transaction *' to 'const Transaction &'
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Mar 7, 2013
Here is the code:
// Creating and joining string objects
#include <iostream>
#include <string>
using std::cin;
using std::cout;
using std::endl;
using std::string;
using std::getline;
// List names and ages
void listnames(string names[], string ages[], size_t count) {
[Code] ....
I may be wrong, but the problem seems to be in the function "listnames". Specifically, the output statement inside the while loop. I don't understand , how the ++ operator is behaving in this statement. The output produced does not match what's printed in the book. I usually just type all the examples, but with this one I also downloaded the source code from the book's website to make sure the error wasn't due to mistyping.
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Nov 12, 2014
This has been bothering me for a while now, and I finally put together an example:
#include <iostream>
#include <string>
using namespace::std;
[Code]....
In the code above, the two classes hold pointers to each other, and that's fine but it doesn't seem right since C++ prefers to pass by reference. Yes, it can still do that (see testbox and testball) but even that seems odd to me because still you need to use pointer notation for the enclosed object. Am I the only one who feels this way, and should I just get over it? Or am I missing something that would allow an object to hold a reference?
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Jun 18, 2013
I have array of pointers and when i tried to assign values dynamically all array items have the same value which is last value.
char* list[];
int DynamicDemo(void)
{
[Code].....
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May 28, 2013
Consider the following:
Code:
int *p;
p = new int[5];
for(int i=0;i<5;i++)
*(p+i)=i;
Now suppose we want to add a 6th element (without using vector)
One way is to copy it across to a larger array:
Code:
int *p;
p = new int[5];
for(int i=0;i<5;i++)
*(p+i)=i;
// realloc
int* temp = new int[6];
std::copy(p, p + 5, temp);
delete [] p;
p = temp;
This looks like a very expensive operation and im looking for other ways.
Three questions regarding the above: Not using vector, is this the best way to do this?What about using realloc? How would I use realloc in this situation?Any other ways apart from realloc or vector?
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Sep 18, 2013
I have created a database for music cds:
Code:
#include<stdio.h>
#include<stdlib.h>
#define array
typedef struct cd_database
[Code]....
When I am using malloc instead of arrays the code is not working properly after exit. I have tried alot but can't came up with a way
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Dec 18, 2014
I would like to realloc a 2D array. I have a counter, itime, it increases each step. Each step, I would like to reallocate my array, keeping the old values, and add new values to the array. When itime=1, I use only malloc, because it is allocated for the first time. When itime increases (e.q. itime=2), realloc comes into process. In the realloc process the GUI crashes.
int itime;
char ** solpointer;
itime = 1;
do {
if( itime == 1 ) {
solpointer = (char**)malloc(sizeof(char*) * itime);
solpointer[itime-1] = (char*)malloc(sizeof(char) * 32);
[code]....
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Jan 3, 2014
I've recently integrated a scripting functionality into my game engine (squirrel), but I can't figure out how to dynamically link the library.I have to dynamically link some libraries for licencing sake, but I'm forced to statically link Squirrel. How can I statically link Squirrel, but dynamically link the others?
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Jul 25, 2014
I'm dynamically creating some labels. This code creates them OK.
panel1.Controls.Clear();
for (int i = 0; i < 5; i++) {
Label label = new Label();
label.Top = (30 * i) + 20;
[Code] ....
Now, after I'm done with them, I'd like to delete them but my code below skips each of the two forloops, so nothing happens. The labels are still on my form. When I debug into this code, I stop on the first forloop and then I step but the flow never goes into the forloop. It jumps to the next forloop where the same thing happens.
List<Label> itemsToRemove = new List<Label>();
foreach (Label label in Controls.OfType<Label>()) {
if (label.Tag != null) {
[code]....
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Sep 8, 2014
I am working on expanding an array and my approach was to do this by copying the array into a bigger array. For this problem I cannot use vectors so what I did was the following:
int *a;
a = new int[5];
for(int i=0;i<5;i++)
*(a+i)=i;
// reallocating array
int* temp = new int[6];
std::copy(a, a + 5, temp);
delete [] a;
a = temp;
Is this approach correct, also how could I implement this on a program to expand an array to double its size or could I not use this to expand an array to double its size?
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Nov 24, 2013
Working on this one from the Jumping into c++ book. The book asks that I create a multidimensional array at run time based on user input and fill it with a multiplication table
My code compiles fine but throws an uninitiated error for p when I try and run it.
Code:
void multiDimentionalMultiplication(int x, int y, int z){
int ***p;
**p = new int[x];
std::cout << "Allocating array.
[code]....
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Jul 26, 2014
I want to access the elements of my array dynamically. So far I've only figured out how to do this manually. if I tried it like this my code would work but there should be a better way right?
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Jun 24, 2014
I have the following dynamically allocated 2D array:
Code:
int num_rows = 100;
int num_cols = 3;
double **myArray= (double**)malloc( sizeof(double *) * num_rows);
for(i = 0; i < num_rows; i++) {
myArray[i] = (double*)malloc( sizeof(double) * num_cols);
}
After sorting the array based on the values in column 1,:
Code:
qsort(myArray, num_rows, sizeof(myArray[0]), comp_function);
int comp_function(const void* a, const void* b) {
double **p1 = (double**)a;
double **p2 = (double**)b;
double *arr1 = *p1;
double *arr2 = *p2;
return arr1[0] - arr2[0];
}
I need to split the array into two halves so that I can pass each separately into another function that accepts a type double ** pointer. What is the most efficient way of splitting the array? Is it possible to keep the original double ** pointer for the first half of the array and then assign a new double ** pointer to the second half of the array?
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Dec 2, 2013
I have declared an array like:
/***********Creating an m*p array**********************/
B = new int *[m];
for(row=0;row<m;++row)
B[row] = new int[p];
How to find the number of elements in it?
The statement
cout << "number of elements in array B equals " << sizeof(B) << endl;
returns 4 each time the program runs
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Jun 14, 2013
I am trying to figure out the syntax to dynamically allocate a single dimension of a triple dimensional array. Basically i have a 2D array of structs. but each struct is an array (basically rows of the information). The rows of this structure need to be allocated dynamically, but the height and width of the overarching structure are static.
Basically: Struct * ts_FieldInfo[100][100] = new Struct[Class.returndataitems()];
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Jan 23, 2013
When I first learned about dynamically allocated arrays in school, I always thought we used them for passing arrays as parameters to functions. But the more I have been practicing coding, I see now that normal arrays can be passed as parameters to functions. So, what is the advantage? Why do we even need them?
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Oct 13, 2014
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].....
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