C++ :: Copying Data Allocated By New Object
Dec 21, 2013
I have an abstract class Base, with derived classes Derived1, Derived2, etc. I don't know how many there are. So, I have declared an object of Derived like so:
Base* der1 = new Derived1(/* constructor details */);
That gets passed to a function, which modified the data contained by this pointer. However, I need to keep the data from the object, which means that I need to copy the data somehow. The problem is, this copying needs to be done within the function, due to the requirements of the program. I do not know what type the object is, This function will need to reset this data potentially hundreds of times, so I can't just provide lots of objects, as either the function will run out of objects to call or I will run out of space in memory.
How would I create a copy of this, so that I would be modifying a temporary object that could be deleted and I would keep the data that I started with?
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Apr 19, 2013
I have a class buffer, which holds a std::string as member, and a socket_receive function:
struct buffer {
string data;
buffer() {}
buffer(buffer& b) : data(b.data) {}
};
buffer socket_receive() {
buffer tmp;
tmp.data = "1234";
return tmp;
}
so when I write
buffer b = socket_receive();
there is a copy constructor, and the tmp variable is constructed and destructed, is there anyway to improve the performance?
I tried the new c++11 move(), but seems even worse, I must be doing wrong with move(), but I don't know how.
#include <iostream>
#include <string>
#include <ctime>
using namespace std;
struct buffer {
string data;
[Code] .....
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Apr 18, 2012
let's say I have an IntPtr that points to the raw data of System.Drawing.Bitmap. is there any way to create a byte array from that IntPtr without copying the data? I'm a pretty experienced C++ programmer, so I can call ToPointer() on it and convert to a byte* to work with it as a pointer, which is no big deal for me, but using a pointer and doing pointer arithmetic increases the risk of bugs, so I'd prefer not to do it that way if there's another way.
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Sep 19, 2014
I used a heap viewer to check for memory leaks. I have many of them and its hard to find out where it is not being freed. Is their a way to use the debugger to log the addresses of the data it allocated on the heap. This way I can trace it back. Or is their any other way to fix memory leaks properly.
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Apr 15, 2014
All i need is to create a "read" function to read all the data for a Player Object.
So Far i made a display function to display all the data for the "Player" object, but i don't know how to make a read function.
Here is my program:
#include <iostream>
#include <string>
#include <vector>
#include <cmath>
#include <cstdlib>
#include <ctime>
#include <iomanip>
#include "player.h"
[Code] .....
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May 24, 2014
How do you create an object (like in the title) something more simple than a struct? I wanna know that cuz I'm writing a function that could return a boolean and an integer at the same time.
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Jan 29, 2015
I've downloaded a Sage 50 2014 data object and added a reference to it in my project. I'm able to connect to the Sage Account package using:
SDOEngine sdoEngine = new SDOEngine();
WorkSpace workSpace = sdoEngine.Workspaces.Add("MyCompany Limited");
try
[Code].....
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Dec 14, 2013
I am writing a program that manages a group of tool bins. This group is handled as an object that is an array of two element structures called InvBin. I initialize the bins with data from a file which contains the descriptions and initial quantities. I also have functions to add or subtract items from a bin and a function to display a report of the description and quantity of all of the bins.
The add and remove functions work correctly based on the cout statement in the functions, however when I display the report, it displays the initial quantity instead of the new quantity. In addition, when I use the add and remove functions again on the same bin, they use the initial quantity.
These are the add and remove functions and the report function from the main program.
Code:
//Adds an item to a bin
void addItem(HANDLE screen, BinManager tools, int &count) {
int binNum;
int addNum;
system("cls");
[Code].....
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Feb 26, 2012
Basically, I've got one object which has to access private data in another object... and can't.
Here's the specifics: I'm writing a little war game program where players deploy units (soldiers, tanks, planes, etc.) onto a gameboard. Players and Units are modeled as objects:
Code:
class GameUnit {
public:
string GetName() {return Name;}
protected:
string Name;
};
class Player {
[Code] ....
Here's the problem: In the above code, Player's ListUnits() function doesn't work because Player can't access GameUnit's GetName() function.
Specifically, here's the compiler's error message:
Code:
In file included from Main.cpp:18:
Player.h: In member function 'void Player::ListUnits()':
Player.h:47: error: 'GetName' undeclared (first use this function)
Player.h:47: error: (Each undeclared identifier is reported only once for each function it appears in.)
I've tested enough to realize that the problem is the GameUnit::GetName() function is a public function within the GameUnit object. Why can't a Player call this function? Making both friend classes of each other doesn't work.
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Nov 12, 2013
How does an object access its private data members in copy constructor.
The relevant part of the code: Code: C::C(const C &obj)
{
x = obj.x;
y = obj.y;
}
Normally the object1 called "obj" cannot access its private data members outside. But in this situation it can access. How can it be explained?
Here are the complete code:
Code:
#include <iostream>
using namespace std;
class C{
public:
C(int,int);
C(const C &);
[Code] .....
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Aug 20, 2013
What is the size of object in c++ , if there is no data member in the class ?
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Mar 19, 2014
#include <iostream>
#include <string>
using namespace std;
class book {
private:
string bookname;
double bookprice;
public:
book(string k="calculus",double b=25.5)
{ bookname=k;
bookprice=b;
}
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Sep 20, 2012
class CPop {
CBSVector<CTour> pop;
CBSVector<double> probability;
int popsize;
double TotalFitness;
CTour Elite;
CTspGAParams GAParameters;
}
error C2059: syntax error : 'constant'
error C2238: unexpected token(s) preceding ';'
I don't know y these errors, it runs fine in simple c++ environment
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Dec 5, 2014
I am trying to read a file use the data line by line to create into an object. The current file I have is like this and the code reading the file will be found below.
1223 Fake1 Name1 60 70 80 24 89 add1 Male
1224 Fake2 Name2 61 70 81 80 24 add2 Male
1225 Fake3 Name3 63 70 82 80 89 add3 Male
1226 Fake4 Name4 63 70 83 80 88 add4 Male
The problem I am having is that I need to put delimiters in the file so that a person can have more than one name and also the address can now hold multiple strings until the delimiter.
I would like to change my file to this;
1223 : Fake1 Name1 : 60 : 70 : 80 : 24 :89 : This will be address1 : Male
1224 : Fake2 Name2 : 61 : 70 : 81 : 80 :24 : This will be address2 : Male
1225 : Fake3 Name3 : 63 : 70 : 82 : 80 :89 : This will be address3 : Male
1226 : Fake4 Name4 : 63 : 70 : 83 : 80 :88 : This will be address4 : Male
How can I update the code below so that it can use the delimiters to create an object?
void loadFile(Person people[], int* i) {
ifstream infile("people2.txt");
if ( !infile.is_open()) {
// The file could not be opened
cout << "Error";
[Code] .....
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Apr 14, 2014
I'm having a problem trying to modify my patient's data. It seems to work, but once the block of code ends it does not save to the linked list.
Problem located in case M.
linked list template header: [URL] ...
patient header: [URL] ...
patient implementation: [URL] ...
#include <iostream>
#include "listTemplate.h"
#include "PatientRecord.h"
using namespace std;
char menu() {
char input
[Code]...
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Jun 26, 2012
I am to first increment data members of object that has not created dynamically (i have done with this part),now i have created object dynamically and how to increment its data which i have passed as argument as:
obj3 = new manage(35 , 36)
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May 16, 2013
Error:
--------------------Configuration: nc - Win32 Debug--------------------
Compiling...
cv.cpp
Linking...
LIBCD.lib(crt0.obj) : error LNK2001: unresolved external symbol _main
Debug/nc.exe : fatal error LNK1120: 1 unresolved externals
Error executing link.exe.
nc.exe - 2 error(s), 0 warning(s)
Compiles with 0 error but on running 2 Errors appear.
I'm Inputting data of an object from user and then inserting it in the link list.
#include <iostream>
//#include <fstream>
using namespace std;
#define LEN 100
////////////////////////////////////////////////////////////////////////////////////////////////////
class employee{
[Code] ....
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Jan 21, 2014
I have two puzzling issues I am dealing with.
Issue 1: I am using a stringstream object in a block of my program that needs to be visited repeatedly depending on a user's selection from a menu. I want the contents of this stringstream object to be cleared any time control gets to this part of the program. I have tried the clear and flush functions to no avail.
Issue 2: I am reading data from a source text file that would be regularly changed during the course of program run. After the program run is over, I am supposed to save the results(which is basically the source text file AND all updates) in a destination file. This destination file would then serve as the source file when next the program is run. In other words, I want a scenario where my results overwrite the original contents of the source file; implying that my source and destination files are now one, pretty much. How can I do this?
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Jun 12, 2013
I'm doing a 1Mb memory dump like this:
Code:
for (int i = 0; i < 0x00100000; i++) {
dump[i] = *(chipmemory+i);
} // i
Then I save the 1Mb "dump" array to a file, and the file contains the data I expect.
The problem arises when I try to write data back to the array beginning at the "chipmemory" pointer:
Code:
unsigned char msga[18] = "SOME MODIFIED DATA";
int address = 172378;
for (int i = 0; i < 18; i++) {
*(chipmemory+address) = msga[i];
address++;
} // i
Is this the correct way to write back to an address 172378 bytes from the "chipmemory" pointer? or is my code broken somewhere else?
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Aug 2, 2012
I have declared two vectors:
std::vector<Class 1> object1;
std::vector<Class 2> object2;
object1 has some value which I want to copy in object2? Is it possible to do?
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Jun 6, 2014
How to make a C function, that will be copying string to the clipboard?(so during execution it copies to cliboard, and after the program ends its execution I will be able to do "Ctrl-V" and paste the things copied)?.
I assume that linux have some sort of in-kernel clipboard which can be filled with some systemcall?
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Apr 23, 2014
how I would code copying a file that cannot be opened (eg. any file that isn't ANSII format).
I know that for a .txt or something like that I could simply do
#include <iostream>
#include <fstream>
#include <string>
[Code].....
how I would copy a file's contents into a char buffer and copy it over to another file for files that can't be opened/read in notepad? (Example: a rar file or a .exe ) Not sure if that makes
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Mar 4, 2013
I'm having some trouble with copying one I/O stream into another. I've put the first one into an array but I cannot get my second prompt to copy the .txt file the first prompt sees and outputs to the console. When I try and grab the info from the .txt file my first prompt sees I only see blank space in my .txt file.
#include <iostream>
using std::cout;
using std::cin;
using std::endl;
#include <fstream>
using std::ifstream;
using std::ofstream;
[Code] .....
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Mar 27, 2014
I'm trying to make a program that will copy all files from one folder in to another folder.
Ex path:
From: G:ExExF1
To: C:EXAll
I'm using Visual studio express C++ as the IDE. I have tried using this code:
bool copy_functions::CopyAll(string InPath,string OutPath) {
ifstream In(InPath.c_str(),ios::in|ios::binary);
ofstream Out(OutPath.c_str(),ios::out|ios::binary);
[Code] ....
But I always get booth could not be opened for copying messages even thug I use the absolute paths for the folders.
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Apr 14, 2013
So I'm writing a function isPalindrome() that can accept a string as an argument, and copy from it only the alphabetic characters in the argument (original) string to another string named alpha_array which contains only the alphabetic characters. Then the function should be able to call the isPurePalindrome function to determine if alpha_array is an ordinary palindrome.
The problem is that when I call isPalindrome in main, the program crashes.
Here's the code I have for isPurePalindrome and isPalindrome:
Code:
/* 1 */
int isPurePalindrome( const char * sentence ) // Can accept strings, array and pointer arguments
{
// Declarations
[Code].....
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Sep 26, 2013
I'm having trouble with this code. What I'm trying to do is to read a line from a file and cut that line into two pieces, one is the keyword and the other is the definition. I want to read up to when there is a dash and assign that line to key and then assign the rest of the line to def. After that I copy key to the struct DictEntries.key and def to DictEntries.def. The output of this shows only the definition for both DictEntries.key and DictEntries.def but if I use "puts(key);" I see the keyword.
Code:
while(!feof(dictionary))
{
char line[200];
char *key,*def;
fgets(line,sizeof(line),dictionary);
key = strtok(line,"-");
}
[code]....
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