I am new C++ and I have a question about separate files classes in Xcode. I did write a program trying to lean class, but I got an error. Could anyone teach me how to do that right ?
I include the program that I tried below
this is the (main CCP):
#include <iostream>
#include "hhhhhhhhhhhhhhhh.h"
using namespace std;
int main ( int argc, char ** argv )
{
bassam bo;
bo.bassamfunction();
}
this is the (.h) :
#ifndef __try_some_concspte__hhhhhhhhhhhhhhhh__
#define __try_some_concspte__hhhhhhhhhhhhhhhh__
#include <iostream>
class bassam{
public:
void bassamfunction();
};
#endif /* defined(__try_some_concspte__hhhhhhhhhhhhhhhh__) */
this is the (CCP):
#include <iostream>
#include "hhhhhhhhhhhhhhhh.h"
using namespace std;
bassam::bassamfunction()
{
cout << " heloo I am here "<< endl ;
}
Your problem is that bassam::bassamfunction() has no return type in the .cpp file. This should be changed to void bassam::bassamfunction().
Related
My code is similar to this one, but the problem is exactly the same: I'm getting an "undefined reference to `Test1::v" in Test1.cpp and in Test2.cpp when compilling the program in VSCode. What am I doing wrong? I'm a bit new on c++ so I just downloaded an extension that made me a project in c++ automatically. When I run the program using Ctrl + Shift + B it gives me this error, but when I do it with the Code Runner extension it doesn't detect the .cpp files.
// Test1.h
#include <iostream>
#include <vector>
using namespace std;
#ifndef TEST1_H
#define TEST1_H
class Test1{
public:
Test1();
static vector<Test1> v;
int a;
};
#endif
//Test1.cpp
#include "Test1.h"
Test1::Test1(){
a = 2;
v.push_back(*this);
}
//Test2.h
#include <iostream>
#include <vector>
using namespace std;
#ifndef TEST2_H
#define TEST2_H
class Test2{
public:
Test2();
double var;
};
#endif
//Test2.cpp
#include "Test2.h"
#include "Test1.h"
Test2::Test2(){
var = 5;
Test1::v[0].a += var;
}
//main.cpp
#include <iostream>
#include "Test1.h"
#include "Test2.h"
using namespace std;
int main(int argc, char *argv[])
{
cout << "Hello world!" << endl;
}
You have declared the static vector in the header file, but you need to define it in a cpp file. Add:
vector<Test1> Test1::v;
to your test1.cpp file. You can learn more about definition vs declaration here.
Also make sure you read this: Why is "using namespace std;" considered bad practice?
You could prepend the class name to call the variable directly since it's static. So, you could do something like:
Test1::Test1(){
// v.push__back(*this); // previous
Test1::v.push_back(*this); // now
}
in Test1.cpp. You'll then get a reference tooltip on your VS Code:
static std::vector<Test1> Test1::v
Which proves it's done.
I am taking a C++ class, and for some reason I can't get the classes in my header file to work on one of my programs. I am using Visual Studio 2017, and I added both my header file and my implementation file together with my test file by using the Solution Explorer in Visual Studio.
I have two constructors in my program, one default and one not. I tried deleting the second one from each file, and the program ran, but I can't get it to work otherwise.
Header File:
#pragma once
class BuckysClass {
public:
BuckysClass();
BuckysClass(string);
void coolSaying();
};
Implementation File:
#include "stdafx.h"
#include <iostream>
#include "BuckysClass.h"
#include <string>
using namespace std;
BuckysClass::BuckysClass() {
cout << "Bucky is ";
}
BuckysClass::BuckysClass(string x) {
cout << x;
}
void BuckysClass::coolSaying() {
cout << "preachin to the choir" << endl;
}
Test File:
#include "stdafx.h"
#include <iostream>
#include <string>
#include "BuckysClass.h"
using namespace std;
int main() {
BuckysClass buckysObject;
buckysObject.coolSaying();
BuckysClass buckysObject2("Bucky is not ");
buckysObject2.coolSaying();
system("Pause");
return 0;
}
syntax error：identifier 'string'
#include <string>//include the string header
class BuckysClass {
public:
BuckysClass();
BuckysClass(std::string);//add the namespace identifier
void coolSaying();
};
Your header file BuckysClass.h does not have the <string> Header file included.
Add:
#include<string>
using namespace std;
you should remove these includes from the corresponding .cpp file and just keep BuckysClass.h in cpp files.
Here are some more pictures of the test file and the error message I got that I couldn't post above.
Test File
Error Messages
I am unsure about the use of separate files for classes. How do I make functions inside the classes? Where do I put it?
QuizMain.cpp:
#include "QuizMain.h"
#include <iostream>
#include <string>
using namespace std;
QuizMain::QuizMain()
{
// Hia stackoverflow
}
QuizMain.h file:
#ifndef QUIZMAIN_H
#define QUIZMAIN_H
#include <string>
using namespace std;
class QuizMain
{
public:
QuizMain();
private:
};
#endif // QUIZMAIN_H
Main file:
#include <iostream>
#include <string>
#include "QuizMain.h"
using namespace std;
int main()
{
QuizMain qm;
return 0;
}
How would I make a class and call it correctly?
This is an example:
QuizMain.cpp file:
#include "QuizMain.h"
#include <iostream>
#include <string>
using namespace std;
QuizMain::QuizMain()
{
// Hia stackoverflow
}
void QuizMain::my_new_function(std::string my_name){
std::cout << "Hi " + my_name +"!" << std::endl;
}
QuizMain.h file:
#ifndef QUIZMAIN_H
#define QUIZMAIN_H
#include <string>
class QuizMain
{
public:
QuizMain();
void my_new_function(std::string my_name);
private:
};
#endif // QUIZMAIN_H
Main file:
#include <iostream>
#include <string>
#include "QuizMain.h"
using namespace std;
int main()
{
QuizMain qm;
qm.my_new_function("foo");
return 0;
}
Anyway, there is no point from asking such a question here. You should probably find a good book/resource and learn how to write and use functions.
Normally you have a header file and cpp file. The header file is where you declare your functions and member variables. The cpp file is where you implement your functions.
quizmain.h
// QuizMain.h file
#ifndef QUIZMAIN_H
#define QUIZMAIN_H
#include <string>
class QuizMain
{
public:
QuizMain(int quizScore);
// declare public functions here
private:
int quizScore; // declare private member variables here.
};
#endif // QUIZMAIN_H
cpp file
// QuizMain.cpp file
#include "QuizMain.h"
#include <iostream>
#include <string>
using namespace std;
QuizMain::QuizMain(int quizScore)
{
this.quizScore = quizScore; // init a quiz score
}
main
Call and create a class object like this
QuizMain quiz(95);
It is easy to do.
If you use the IDE project, the IDE set you to use the any file. Like code::block IDE But if you do not use the IDE project it is a little different to use.
You should write the .h file and then,after all writing you should put .cpp file.
Also you can use interface class that works by poiter.
/// .h file and declaration
#ifndef ONE.H
#define ONE.H
class one {
public:
one();
~one();
};
#include "one.cpp"
#endif ONE.H
then:
/// .cpp file and implementation
one::one(){
std::cout<<"constructor one"<<std::endl;
}
one::~one(){
std::cout<<"destructor one"<<std::endl;
}
then :
#include <iostream>
#include "one.h"
int main()
{
one o;
}
output:
constructor one
destructor one
Process returned 0 (0x0) execution time : 0.010 s
Press ENTER to continue.
I try to compile my code, I pretty sure I made a mistake in my headers or in the compilation but I don't understand where. I know that this is a basic problem, and I read some other topic, but I really don't understand. And I watch some other code I wrote and I don't see any difference...
g++ -c main.cpp -o out
I don't understand the error, so I also try :
g++ -c readFastqFile.cpp
The error
readFastqFile.cpp:8:1: error: ‘readFastq’ does not name a type
readFastq::readFastq(){ //Constructor
And my files are :
main.cpp
#include <iostream>
#include <string>
#include "readFastqFile.hpp"
using namespace std;
int main(int argc, char *argv[]){
cout << "hello" <<endl;
//readFastq allReads;
return 0;
}
readFastqFile.hpp
#ifdef READFASTQFILE_HPP
#define READFASTQFILE_HPP
#include <iostream>
#include <string>
using namespace std;
class readFastq{
public:
readFastq(); //constructor
private:
string readName;
string sequence;
string score;
};
#endif // READFASTQFILE_HPP
readFastqFile.cpp
#include <string>
#include <iostream>
#include "readFastqFile.hpp"
using namespace std;
readFastq::readFastq(){ //Constructor
readName = "bla";
cout << readName <<endl;
}
Thanks
#ifdef READFASTQFILE_HPP should be #ifndef READFASTQFILE_HPP. The #ifdef is causing the contents of readFastqFile.hpp to be ignored, so the class definition isn't being compiled.
See also Include guards
I'm a pretty seasoned programmer but I'm just now diving into C++ and it's... well... more difficult than PHP and Python. I keep having unresolved external errors when trying to create an object from some classes. It's broken up into multiple headers and files but here is a basic idea from one of my classes:
die.h:
#ifndef DIE_H
#define DIE_H
using namespace std;
class Die {
public:
int throwDie();
Die();
};
#endif
die.cpp
#include <iostream>
#include <cstdlib>
#include "Die.h"
using namespace std;
int Die::throwDie()
{
return 0;
}
sixsidedie.h
#ifndef SIXSIDEDIE_H
#define SIXSIDEDIE_H
#include "Die.h"
using namespace std;
class SixSideDie : public Die
{
public:
SixSideDie();
int throwDie();
private:
int randNumber;
};
#endif
sixsidedie.cpp
#include <iostream>
#include <cstdlib>
#include <time.h>
#include "Die.h"
#include "SixSideDie.h"
using namespace std;
const int SIX_SIDE = 6;
int SixSideDie::throwDie()
{
srand((unsigned int)time(0));
SixSideDie::randNumber = rand() % SIX_SIDE + 1;
return SixSideDie::randNumber;
}
main.cpp
#include <iostream>
#include <cstdlib>
#include "Die.h"
#include "SixSideDie.h"
#include "TenSideDie.h"
#include "TwentySideDie.h"
using namespace std;
int main()
{
Die* myDice[3];
myDice[0] = new SixSideDie();
myDice[1] = new TenSideDie();
myDice[2] = new TwentySideDie();
myDice[0]->throwDie();
myDice[1]->throwDie();
myDice[2]->throwDie();
system("pause");
return 0;
}
It keeps telling me that each object I create directly above is an unresolved external symbol and I just don't know why. Any thoughts!?
You declared a constructor for Die but never defined it.
Also, you almost certainly want throwDie to be virtual if you intend to override its behavior in derived classes, and you should never use using namespace std; in a header file (and many people, including me, would argue that you shouldn't use it at file-scope at all).
You didn't define your constructor in your cpp files.
Its good practice to define the constructors of the classes. Check this out:
#ifndef DIE_H
#define DIE_H
using namespace std;
class Die {
public:
int throwDie();
Die() { }; // can you spot the difference here?
};
#endif