C++ :: Size Of Object If There Is No Data Member In Class
Aug 20, 2013What is the size of object in c++ , if there is no data member in the class ?
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C++ :: Using Member Function Of A Class In Another Class And Relate It To Object In Int Main
Aug 21, 2013I am writing a program which is using SDL library. I have two different classes which one of them is Timer Class and the other is EventHandling Class.
I need to use some member functions and variables of Timer in some Eventhandling Class member functions, Although I want to define an object of Timer in int main {} and relate it to its member function that has been used in Eventhandling member function in order that it becomes easier to handle it, I mean that I want to have for example two objects of timer and two objects of Eventhandling class for two different users.
I do not know how to relate an object of a class from int main{} to its member function which is being used in another class member function.
Lets have it as a sample code:
class Timer {
private:
int x;
public:
Timer();
get_X();
start_X();
[Code] ....
C++ :: How To Get Object Of Original Class From Function Of Other Class Where Other Class Object Is Member Of Original Class
Jan 21, 2013The case is like
class B{
public:
somedata;
somefunction();
}
class A{
public:
data;
function();
}
in somefunction i want a pointer to current object of class A m new to c++
C/C++ :: Size Of Class When Char Member Added
May 25, 2014Why is the size of an empty class 1? Why is the class still one when I add a char member to the class?//using turbo c++ 3.0, yes I know I'm using a very old c++ compiler and software
View 3 Replies View RelatedC/C++ :: Object Of Arrays As A Private Data Member?
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;
}
Visual C++ :: Object As Data Member Having Error
Sep 20, 2012class 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
C++ :: Size Of Object Of Class Child?
Feb 5, 2014hiclass Parent {
};
class Child : virtual public Parent {
};
What is the size of object of Class Child in following case?
C++ :: Store Reference To Const Object In Class As A Member Variable?
May 27, 2014i want to store reference to a const object in my class as a member variable, as follow:
I basically want a readonly reference to |Data| in Device object.
Code:
class Device {
Device(const QList<QSharedPointer<Data>> & dataList) : _listRef(dataList) {
} protected:
const QList<QSharedPointer<Data>> & _listRef;
}
This does not allow me to initialize _listRef as something like NULL when it is not applicable.Also, i must change all my constructors and its child class to include an initialization of _listRef!!
What is the alternative? Is pointer the nearest? which of the following should be used?
Code:
const QList<QSharedPointer<Data>> * _listRef;
or
const QList<QSharedPointer<Data>> *const _listRef;
or
const QSharedPointer<QList<QSharedPointer<Data>>> _listRef; ????
C++ :: Class Data Member Access?
Jul 5, 2013I have some doubt regarding class data member accessing in another file.Follwing code showing error.
class A://file a.cpp
{
public:
int add;
int sub;
};
//file b.cpp
extern class A
void cal()
{
A::add=A::sub;
}
C++ :: Make A Class Without Any Data Member?
Aug 18, 2013can we make a class without any data member ? but it may have member functions ! in c++
View 2 Replies View RelatedC/C++ :: Vector As A Member Data Of Class
Dec 30, 2013If I want a class with a vector data member, can I specify it as follows?
std::vector< bool > integers( 101 )
I'm having some problems when compiling code.
C/C++ :: Make Class Without Any Data Member?
Aug 18, 2013is this possible to make a class without any data member in c++ ?
View 1 Replies View RelatedC++ :: Class Constructors And Data Member Initialization
Oct 29, 2014I recently discovered the new - new to me anyway! - feature of modern C++ that allows you to set the initial value of a data member when you declare it:
class CINTWrapper{
private:
int m_iData=0;
};
This even extends to calling member functions that work with initialization I believe:
class CStringWrapper{
private:
wchar_t* Allocate_Array(const int iBufferSize);
wchar_t* m_pString=Allocate_Array(1);
};
At first, this seemed an extremely useful piece of functionality that C++ had been lacking all along. However, the more I thought about it the more it struck me this feature actually undermines one of the principle design elements of the language - that being the Constructor.
As I understand it the primary purpose of the Constructor is specifically to give the programmer a place where it is guaranteed he can always initialize his data members before anything else is done with the class. However, given the new initialization rules this is no longer necessary. So it largely seems to me that Constructors as a whole are no longer necessary either! Copy-Constructors are a special and vital case. Admittedly when I was using them for their intended purpose I hated either the redundancy you had to introduce across multiple Constructors; those with and without arguments and so on, or alternately the fine tuning of helper-functions to do common initialization between these variants. Now however I sort of regret this cast-iron rule has been taken away.
As a last point, I am trying to change the way I think about programming. I am trying to employ more objects than pure C-style ('int' or 'double', etc) data types and especially to move into templates (although absolutely NOT the Hewlett Packard template library!). Given my current understanding of inheritance in particular it seems to me that using pre-initialized data members rather than Constructor-initialization makes object derivation even more complicated, not less so.
C++ :: Member Data Defined In Base Class?
Jul 25, 2012Let's take a look at the code first,
Code:
class B
{
public:
int data;
};
class D : public B
{
public:
int data;
};
Both B and D defines data. I wonder if there is any difference between them?
C++ :: Zero Init Data Member Of Class In Header File
Jan 9, 2014I have a small class with a static int data member. I want to zero init it. I am thinking that making a .cpp file with only one line seems too much, isn't it?
So, can I do it inside the the header file? The variable is going to enumerate how objects were created (so any alternative will do).
C++ :: Can't Initialize Static Data Member In The Class Definition
Apr 17, 2013"You cannot initialize the static data member in the class definition — that’s simply a blueprint for an object and initializing values for members are not allowed. You don’t want to initialize it in a constructor, because you want to increment it every time the constructor is called so the count of the number of objects created is accumulated."
Why don't you want to initialize it in a constructor?
Edit: Because every time it is called it will set it back to 0 or whatever the initializing value.
C++ :: Multiple Data Streams In One Class - Handling All In One Member
Jan 24, 2014I have to implemente the to_string method. Whats the fastest way? Stringstreams. But I have to use C++ without any headers, so I need to implement the stringstream class. How can an stringstream hold one float? An double? Hoq cqn I implement an strigstream myself?
View 8 Replies View RelatedC++ :: How To Define Static Member Data In Abstract Class
Jul 11, 2012For example, in a header file A.h, I define an abstract class,
Code:
// A.h
class A {
public:
virtual void foo() = 0;
private:
static int _x;
};
How'd I initialize static member data _x?Normally, we initialize a static member data in a cpp file. However, there is not cpp file for A.h. If I intialize _x in header file, there will be linker errors like mulitple defined symbols. What is appropriate way to do that?
C++ :: How To Create A Base Class Which Defines Static Data Member
Sep 9, 2013Basically I want to create a base class which defines a static data member so that its automatically redeclared as the same static data member in the derived class.
class A{
protected:
static derivable int val;
// A::val
}
class B : public A{
// static derivable int val is already here
// A::val AND B::val
}
This seems impossible to me but I'm wondering if perhaps there's a way to add modifiers to the compiler to do this (or preferably something MUCH simpler)...
C/C++ :: Error Header Has No Member Named Size
Dec 1, 2014Was missing the '.s'
I'm getting this error in the 'my_free' function here "bp->s.size += p->s.ptr->s.size;" and "p->s.size += bp->s.size;" here. This doesn't make sense to me because it seems to be the correct way to access the union, and In the "my_malloc" function I use a similar call "p->s.size = nunits;" and that works fine.
// gcc -o malloctest -Wall -g -ldl main.c
// ./malloctest
#include <stdbool.h>
[Code].....
C# :: Object Header Size?
Dec 25, 2014In 32bit, the object header size is always 8bytes.
In 64bit, the object header size is always 16bytes.
Is this safe to assume or are there situations where the header size can be smaller/larger than the numbers above?(Haven't found anything on this, so I assume no?)
I need to know the exact size of the object header, because I need specifically pad a few classes I wrote to avoid false sharing along cache lines. Just need to make sure I have the sizes correct so I don't pad them wrong!
C++ :: Importance Of Static Object In A Class And How They Are Different From General Object
Dec 13, 2012#include "B.h"
class A {
public :
A()
{
s_b = new B();
b = new B();
[Code] ....
In my project i have seen static object as above . But not able to know what is the exact use of it and how they are different from general object .
Visual C++ :: How To Reduce Size Of Object
Feb 10, 2014I am using Visual C++ to write an app. I write CMyObject class and may allocate a lot of instances of CMyObject object, so I want to reduce the size of CMyObject class.
What I can figure out to do is:
1. I can use the following code to get the accurate size used by a single instance of CMyObject object:
CMyObject Object;
//Get the size of memory allocated for CMyObject object
int nSize = sizeof(Object);
is that correct?
2.To reduce the size of CMyObject, I have several ideas:
(1)Change member function to static member function if it is possible, since each member function will take some spaces in the instance of CMyObject.
(2)Change virtual member function to member function if it is possible, since virtual member function may take more spaces.
(3)Eliminate unnecessary member variables to reduce spaces.
(4)Finally, if (1), (2) and (3) does not work well, then change CMyObject from class to a struct that only contains some member variables, thus will eliminate the spaces allocated for constructor and destructor of a class.
C/C++ :: Unexpected Behavior For Classes That Contain Member Object
Apr 1, 2014I have a WordRecord that contains a LinkedList (both my doing). I have rigorously tested my LinkedList class, and know that it works (heck, I used it in the last project I had!). The problem is that undefined behaviour seems to happen when using the WordRecord, which has a std::string and a LinkedList<unsigned>. (The problem happens with the LinkedList.)
Here is the code:
main.cpp
#include <iostream>
#include "BinaryTreeNode.h" // here for test purposes
#include "LexicographicTree.h"
#include "LinkedList.h"//also for test purposes
#include "OutputStream.h"
#include "WordRecord.h"
using namespace std;
int main()
{
// setup the OutputStream to print to "test.txt"
OutputStream stream("test.txt");
// create a sampleWordRecord (make it have the word "I" on line 1)
[code]....
One of the requirements for the project is that it must compile on Unix server (I am using Windows, and have tested it in both environments.) I get a core-dump in the Unix environment. On the other hand, the output on-screen in the Windows environment looks right. However, when I open up the text file, I get the following
Sample word record:
WordLines
I{14}
/* I have no what is happening to sampleWordRecord's LinkedList; I am not trying to modify it, except for where I created the sampleWordRecord! */
C/C++ :: Object File Size Increases In Windows?
Apr 11, 2013My sample.h is
#include <string>
namespace xxx
{
class abc
[Code]....
My Question is when i compile this code in Linux platform Using g++ compiler My sample.o's Size is 1Kb.. But when the same code is compiled in Windows platform using VC++ Compiler , My sample.o's size is 42Kb..to reduce the size in windows... Is there any proble with '#include <string>' in Windows platform.
C++ :: Calling Member Function By Object Pointer
Nov 26, 2013I have the following piece of code.
Code:
#include<iostream>
using namespace std;
class Test {
public:
Test(){cout<<"Test"<<endl;}
void fun() {
int i=5;
[Code] ...
Compiled with g++.
Executing this give output fun5.
It is correct? I have not allocated any object and so this pointer is not created. Then how it is able to run and call the function.