I 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).
at my work we use a static analysis tool and it is pointing out some uninitialized variables. One of which is a class member variable which is a C struct. Now, that variable is already declared in the header file for the class.
Currently in the class constructor I am doing:
Code:
memset( &thestruct, 0, sizeof( thestruct ) );
Is there a C++ way to do this? I Googled this but all I really found was:
Code:
StructDef thestruct = {};
Which doesn't really apply here.
I'm trying to use a class member to initialize the dimension of a matrix. I have two issues. Here is the code (.h) simplified :
#include <vector>
#include <array>
#include <typeinfo>
template<typename T, std::size_t N>
struct md_vector {
[Code] ...
error: invalid use of non-static data member ‘OptimalSamplingStrategy::_nbMorph’|
I can't use a class member directly in the header file (here _nbMorph).
It was an issue I got before and that I didn't solve as I succeed in finding other ways. I don't think it's possible here.
I am currently doing the assignment about linked list. Here are some details information about what I am doing.. This program is C++ and should run on Visual Studio 2010. And it contains three file, two datastructure header and one main cpp file.
This program is trying to arrange and show some sports records. The main program which contain the functions such as reading the result text file(each result text file contain several records of athletes), removing a file, arranging the totalresult and printing it out. And the main program is already given and I cannot overwrite it.
But when I finished and try to build the solution and run it, I am not able to run the program and it give me somethings like these...
warning C4172: returning address of local variable or temporary
error C2248: 'Datastructure1::Datastructure1' : cannot access private member declared in class 'Datastructure1'
see declaration of 'Datastructure1::Datastructure1'
see declaration of 'Datastructure1'
This diagnostic occurred in the compiler generated function 'Result::Result(const Result &)'
And I have tried to comment each function part of the header file and see if can run or not. But I still fail to do so. Here are my codes...
#ifndef DATASTRUCTURE1_H
#define DATASTRUCTURE1_H
class Datastructure1 {
Public:
Datastructure1( );
[Code] ....
There are two header files and look quite long. They are all some linked list functions . I have read and learn linked list data structure before I complete this programs. However, when I complete the functions required, the function cannot be compile....
I get the following error in XCode whenever I try to access the member I created 'randomGen' in a separate class in a different header file. I have made sure to include the header file and have tried to access it through an object.
This is the code I enter when trying to access the method from randomiser.h in main.cpp. It is also an overloaded function with doubles and integers:
RandomG randomiser;
randomiser.randomGen(); // 'Call to member function 'randomGen' is ambiguous'
This is the code inside randomiser.h:
#include <string>
#include <iostream>
using std::string;
using std::cout;
using std::endl;
class RandomG {
[Code] ....
This is the error inside xcode: [URL] ....
I have tried seperating the code for the functions in another class (main.cpp) and then running and it seems to works, so I'm not sure why I can't put everything in the .h file and then access it?
I would like it in a seperate file so it doesn't clutter my main. I am writing a game with SDL so that might be confusing and I would like the window to have a random title and other random properties, so it would be easier to use a function.
I 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;
}
can we make a class without any data member ? but it may have member functions ! in c++
View 2 Replies View RelatedIf 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.
is this possible to make a class without any data member in c++ ?
View 1 Replies View RelatedI 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.
What is the size of object in c++ , if there is no data member in the class ?
View 3 Replies View RelatedLet'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?
"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.
I 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 RelatedFor 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?
Basically 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)...
I wrote a simple date class and could not get it to work until I put all the code in main(). Then it worked like a charm. I have not been able to create a separate .cpp file and get it to work with my existing main().
I tried to follow [URL] which is a closed article, with no success. I tried every combination I could think of and was unable to compile without error. (Linux Mint 17,code::blocks 13.12, G++ 4.8.2). I did finally get it to work by putting *all* my code in the .h file and #including the .h file (and nothing else) in the .cpp file. This is not how it's supposed to work.
This is unbelievable! I just tried this on another computer, same OS same version of Code::Blocks and G++.
I am working on an assignment in which i have to perform th following task
myClass itsObject1,itsObject2;
itsObject2=5000+itsObject1;
I have defined overloaded operator as follows in the header file but in the cpp file of the class it gives error.
friend vli &vli::operator + (int &a,vli &obj);
How to define it in cpp file of my class?
What is the right syntax for implementing the .cpp of a template class?
Consider this LinkedList.h file:
Code: #include<iostream>
#include"Iterator.h"
template <class T>
class LinkedList {
[Code] ....
How should the implementation for the LinkedList constructor, for example, should look like in the LinkedList.cpp file?
I tried this:
Code: #include "LinkedList.h"
template <class T>
LinkedList<T>::LinkedList<T>() {
// constructor
}
LinkedList<T>::~LinkedList<T>() {
// destructor
}
But the compiler wouldn't accept it.
lets say we have a valid class with full implementation, X. can this class be declared as forward in Y header file:
Code: class X;
class Y{
X* m_X;
}
but still be used as regular in the cpp file?
Code:
#include "Y.h"
#incldue "X.h"
T Y::function(){
m_X->doSomething();
}
visual studio prevents me from doing it , I wonder if the standard also says so.
In the code given below using turboc++ 3.0(really old i get it but its school rules)
#ifndef emoji_h
#define emoji_h
class emoji//here for some reason {
};
#endif
error i get :line 3 declaration syntax error why and how to correct it?
I have been working a project in C++. I have TTTMain.cpp file that has all the function calls, TTTFuntions.cpp that has all the functions, I have TTT.h file that has all the prototypes and variables and additionally I have Winner.h that has enum class Winner declaration in it. Here is my block of codes:
Winner.h file:
#ifndef winner
#define winner
enum class Winner {
[Code]....
My question is when I compile this gives me error on
Winner gameSquares[] = { Empty, Empty,Empty, Empty, Empty, Empty, Empty, Empty, Empty };
with saying "invalid use of non-static data data member" and It says "Empty was not declared in this scope."
I know calling enum is very very trick.
I have a header file that declares some fields as private, I then have a class that I need to compare two of the objects' information for equality but neither of them are the calling objects. I cannot alter the header file. How would I go about comparing private data fields? I will enter a brief bit of code for clarity.
Code: // Header File
// stuff.h
class stuff
{
private:
int* arr[20];
int size;
};
bool equal (const stuff& a, const stuff& b);
[code].....
I'm trying to read from a header file to take the image dimensions and other variables but I don't understand how to iterate through the "key" so it saves each line.
This is what the header file will always look like:
!INTERFILE :=
!imaging modality := nucmed
!version of keys := 3.3
;
!GENERAL DATA :=
[Code].....
Ideally it would just skip the keys that aren't wanted and keep moving through the lines. Should there be a for loop for the key (and if so, how does that work with pointers?) or should this method just be scratched...
Here's my class/header, and Visual studio Output.
Injection point/instantiation.
int main() {
Player player;
Call to a public method:
while(!isWin("x", board) && !isWin("o", board) && whoGoesFirst == "p") {
printBoard(board);
board = player.playerTurn(board);
[Code] .....
Output:
1234
1
1> Player.cpp
1>c:users
sccdocumentsvisual studio 2012projectsprog 2100 - assignment 1prog 2100 - assignment 1player.h(10): error C2143: syntax error : missing ';' before '<'
1>c:users
sccdocumentsvisual studio 2012projectsprog 2100 - assignment 1prog 2100 - assignment 1player.h(10): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
1>c:users
sccdocumentsvisual studio 2012projectsprog 2100 - assignment 1prog 2100 - assignment 1player.h(10): error C2238: unexpected token(s) preceding ';'
I have a header file with a bunch of functions. I want to create a thread using the <threads> package and am using
void myclass::functionX() {
}
void myclass::function() {
std::thread tr(myclass::functionX);
}
I am getting the error "no instance of std::thread::thread matches the argument list argument types are (void());