I'm new to C++ and using namespaces and I can't see what I'm doing wrong here. When I compile the code below, I get the error:
error: 'Menu' has not been declared
Here is my header file Menu.hpp
#ifndef MENU_H //"Header guard"
#define MENU_H
namespace View
{
class Menu
{
void startMenu();
};
}
#endif
and my Menu.cpp:
#include "stdio.h"
using namespace std;
namespace View
{
void Menu::startMenu()
{
cout << "This is a menu";
}
}
You missed including the header file which defines the class.
Menu.cpp:
#include "Menu.hpp"
Each translation unit is compiled separately by the compiler and if you do not include the header file in Menu.cpp, there is no way for the compiler to know what Menu is.
You will have to include header Menu.hpp in your cpp file Menu.cpp like
#include "Menu.hpp"
Related
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
So I've done extensive googling and searching on StackOverflow and am unable to find a solution despite several answers with this exact issue.
I am trying to create a test class in an external file called Fpc5.cpp
It's contents are:
Fpc5.cpp
#include "stdafx.h"
#include "Fpc5.h";
#include <iostream>
using std::cout;
class Fpc5 {
int bar;
public:
void testMethod();
};
void Fpc5::testMethod() {
cout << "Hey it worked! ";
}
and my main .cpp file:
Test.cpp
// Test.cpp : Defines the entry point for the console application.
//
#include "stdafx.h"
#include "iostream"
//#include "Fpc5.cpp"
#include "Fpc5.h";
using std::cout;
using std::cin;
using std::endl;
int main()
{
cout << "Hello" << endl;
Fpc5 testObj;
testObj.testMethod();
system("pause");
return 0;
}
all the answers I've read indicate this is caused becaused I used to be including the class in the main file itself which is why I created a header file
Fpc5.h
#pragma once
void testMethod();
This changed the error, but still did not fix the issue. Currently my Test.cpp does not recognize a Fpc5 class. I've also tried adding the Fpc5.cpp and Fpc5.h in stdafx.h and that still does not resolve the issue.
stdafx.h
// stdafx.h : include file for standard system include files,
// or project specific include files that are used frequently, but
// are changed infrequently
//
#pragma once
#include "targetver.h"
#include <stdio.h>
#include <tchar.h>
// TODO: reference additional headers your program requires here
//#include "Fpc5.cpp"
#include "Fpc5.h"
I'm sure this a simple syntax/conceptual understanding error, but I'm quite new to c++ and am not sure what is wrong.
This is definition of your class and it must be in Fpc5.h
class Fpc5 {
int bar;
public:
void testMethod();
};
Then, you have Fpc5.cpp where you implement methods of the class:
#include "Fpc5.h" // Compiler needs class definition to compile this file!
void Fpc5::testMethod()
{
}
And then you can use Fpc5 class in Test.cpp
#include "Fpc5.h"
int main()
{
Fpc5 foo;
foo.testMethod();
return 0;
}
As an alternative you can pack everything into Test.cpp
Move the definition of your class:
class Fpc5 {
int bar;
public:
void testMethod();
};
to the header file, "Fpc5.h".
Implement the methods to "Fpc5.cpp".
I have already checked StackOverflow to find the solution to my problem, but I think I might be missing something. I am trying to define a class in a header file (.h) and implement its methods in a cpp file (.cpp), but it does not work.
main.cpp:
#include <iostream>
#include "Message.h"
using namespace std;
int main()
{
Message *t = new (Message);
t->display();
return 0;
}
Message.h:
#ifndef MESSAGE_H_INCLUDED
#define MESSAGE_H_INCLUDED
class Message {
public:
void display();
};
#endif // MESSAGE_H_INCLUDED
Message.cpp:
#include "Message.h"
void Message::display() {
cout << "Hello!";
}
I don't understand why I keep getting the following error
undefined reference to 'Message::display()'
Compile this with the command g++ -std=c++11 Message.cpp main.cpp
I have been having a lot of trouble with my headers and making sure everything is declared correctly. First off my files:
//Main.cpp
#include "Item.h"
#include "Warehouse.h"
using namespace std;
int main() {
...
}
//Item.h
#ifndef ITEM_H
#define ITEM_H
#include <string>
using namespace std;
class Item {
...
};
#endif /* ITEM_H */
//Item.cpp
#include "Item.h"
//Warehouse.h
#define WAREHOUSE_H
#ifndef ITEM_H
#define ITEM_H
using namespace std;
class Item;
class Warehouse {
...
private:
Item* array; //problem starts with this
};
#endif /* WAREHOUSE_H */
//Warehouse.cpp
#include "Warehouse.h"
#include "Item.h"
Warehouse::Warehouse() {
array = new Item[arraySize]; //and this is where I get the error
}
I am pretty sure the problem has to do with my header in Warehouse.h but every combination I try does not work. Sorry if not enough of the code is posted but I figure the problem is with the includes and declarations.
Thanks ahead of time.
edit: to clarify this is not in one file. I just wrote it like this to simplify things. Each one of the above is a separate file.
Your include guards in the header file Warehouse.h are not correct.
Instead of
//Warehouse.h
#define WAREHOUSE_H
#ifndef ITEM_H
#define ITEM_H
using namespace std;
// ...
#endif /* WAREHOUSE_H */
you want
//Warehouse.h
#ifndef WAREHOUSE_H
#define WAREHOUSE_H
using namespace std;
// ...
#endif /* WAREHOUSE_H */
With the current version the class definition in item.h is never included in Warehouse.cpp because the mixed-up include guards in Warehouse.h prevent item.h to be read due to the order of
//Warehouse.cpp
#include "Warehouse.h"
#include "Item.h" //Warehouse.cpp
#include "Warehouse.h"
#include "Item.h"
Then the compiler does not know the definition of Item at that point, hence the error.
Another thing: Do not form the habit of using namespace std in header files. This will lead to issues at some point.
Problem is not in this declaration
private:
Item* array; //problem starts with this
You may define a pointer to an incomplete type.
I think the problem is in a statement where you try to allocate an object for this pointer using operator new or to dereference the pointer.
Also I do not see any reason why you do not want to include header Item.h in header Warehouse.h instead of using elaborated name
class Item;
I am getting errors with the following code. The errors are incomplete type is not allowed and use of undefined type 'mGame'.
header.h:
//--Libraries
#include <stdlib.h>
#include <stdio.h>
#include <time.h>
#include <iostream>
#include <string>
#include <sstream>
using namespace std;
//--Classes
class mGame;
Game.cc:
#include "header.h"
class mGame
{
private:
public:
bool intro();
};
Intro.cc:
#include "header.h"
bool mGame::intro() //--Line 3
{
printf("|-----------------------------|\n");
printf("\n Welcome to the Guessing Game!\n");
printf("\n|-----------------------------|\n");
return false;
}
The errors are both on line 3 of intro.cc. I tried finding a solution, but I couldn't for what I am doing.
header.h doesn't know any definitions of game.cc, you tell header.h only, that there is a class mGame. rename game.cc to game.h and include it into header.h and delete the line "class mGame;"
To be able to use mGame from Intro.cc, you have to move the class declaration into header.h (or into some other header file that you include from Intro.cc).
Having a forward declaration in header.h is not enough (that's what is meant by "incomplete type is not allowed").