Creating a .h file

[Yom]

Help,

I am a beginner with C++, taking a class right now. The lab this week is to create a user defined class and have it accesses in a seperate .h header file from the main.

I think I'm finding my way through it, but I'm getting a complie error that makes no sense to me:

1> Resistor.cpp
1>c:\users\tom\documents\school\comp 220\week 2\lab\lab 2.2\lab 2.2\resistor.h(11): error C2146: syntax error : missing ';' before identifier 'resistor'
1>c:\users\tom\documents\school\comp 220\week 2\lab\lab 2.2\lab 2.2\resistor.h(11): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
1>c:\users\tom\documents\school\comp 220\week 2\lab\lab 2.2\lab 2.2\resistor.h(11): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
1>c:\users\tom\documents\school\comp 220\week 2\lab\lab 2.2\lab 2.2\resistor.h(14): error C2061: syntax error : identifier 'string'
1>c:\users\tom\documents\school\comp 220\week 2\lab\lab 2.2\lab 2.2\resistor.h(20): error C2146: syntax error : missing ';' before identifier 'getResName'
1>c:\users\tom\documents\school\comp 220\week 2\lab\lab 2.2\lab 2.2\resistor.h(20): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
1>c:\users\tom\documents\school\comp 220\week 2\lab\lab 2.2\lab 2.2\resistor.h(20): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
1>c:\users\tom\documents\school\comp 220\week 2\lab\lab 2.2\lab 2.2\resistor.h(20): warning C4183: 'getResName': missing return type; assumed to be a member function returning 'int'
1>c:\users\tom\documents\school\comp 220\week 2\lab\lab 2.2\lab 2.2\resistor.h(21): error C2061: syntax error : identifier 'string'
1>c:\users\tom\documents\school\comp 220\week 2\lab\lab 2.2\lab 2.2\resistor.h(22): error C2061: syntax error : identifier 'string'
1>c:\users\tom\documents\school\comp 220\week 2\lab\lab 2.2\lab 2.2\resistor.h(23): error C2061: syntax error : identifier 'string'
1>c:\users\tom\documents\school\comp 220\week 2\lab\lab 2.2\lab 2.2\resistor.h(29): error C2061: syntax error : identifier 'string'
1>c:\users\tom\documents\school\comp 220\week 2\lab\lab 2.2\lab 2.2\resistor.h(30): error C2065: 'res1' : undeclared identifier

//

Here is the first portion of the .h file:

/
#include <iostream>
#include <iomanip>
#include <Windows.h>
#include <math.h>
#include <string>

class CResistor	{

	double res1, res2, res3, percentage, Nominal, Tolerance;
	bool tf;
	string resistor;

public:
#include <iostream>
#include <iomanip>
#include <Windows.h>
#include <math.h>
#include <string>

class CResistor	{

	double res1, res2, res3, percentage, Nominal, Tolerance;
	bool tf;
	string resistor;

public:
/

Any help would be greatly appriciated!

[BinaryGeek]

You only need the #includes one time in a header file. Second, there's no need to declare the class twice with the same stuff. But here's what I did for you for defining the class.

#ifndef CRESISTOR_H	// Include this so the class is not called more than once.
#define CRESISTOR_H     // Also include the define.

#include <iostream>
#include <iomanip>
#include <Windows.h>
#include <math.h>
#include <string>
using namespace std;	// You forgot this

class CResistor	
{
	private:  // You forgot to declare private (or protected if that's your case)
		double res1, res2, res3, percentage, Nominal, Tolerance;
		bool tf;
		string resistor;

	public:
	// Your public definitions.

};	// Don't forget the semicolon
#endif	// Gotta include this at the end. 

[Yom]

Thanks very much, I have another question if you don't mind. For some reason in main when I try to declare an object for the class CResistor it gets an error.

Here is the class code now

#ifndef CRESISTOR_H	
#define CRESISTOR_H 

#include <iostream>
#include <iomanip>
#include <Windows.h>
#include <math.h>
#include <string>

using namespace std;

class CResistor	{

	double res1, res2, res3, tolerance, Nominal;
	bool fnDisplay;
	string resistor;

public:
	CResistor (double, double, string, bool); 
	void resObj (double, bool);
	double getNominal (bool);
	void setNominal (double,bool);
	double getTolerance (double);
	void setTolerance (double, bool);
	string getResName (bool);
	void Res1 (double, double, string, bool);
	void Res2 (double, double, string, bool);
	void Res3 (double, double, string, bool);
	void DisplayResistance(double,double, double, bool );
};
#endif 

Here is the peice of main where I am trying to declare " resObj " and the error.

void main(void)
{

 //Control variable to display function names when called
 bool fnDisp = false;
 CResistor resObj;
 CResistor Res1(4700.0, 0.10, "Res1", fnDisp);
 CResistor Res2(330.0, 0.10, "Res2", fnDisp);
 CResistor Res3(10000.0,0.10, "Res3", fnDisp);

 DisplayResistance(Res1, fnDisp);
 DisplayResistance(Res2, fnDisp);
 DisplayResistance(Res3, fnDisp);
  
 EnterResistance(Res1, fnDisp);
 DisplayResistance(Res1, fnDisp);

 system("pause");
}

1>c:\users\tom\documents\school\comp 220\week 2\lab\lab 2.2\lab 2.2\my first class.cpp(69): error C2512: 'CResistor' : no appropriate default constructor available

??

[BinaryGeek]

Try CResistor(); for your default constructor. You're also going to need your implementation file (functions). Example would be like...

void CResistor::DisplayResistance(double, double, double, bool)
{
//your function code.
}

Oh and don't forget the #include "CResistor.h" for every file.

[Yom]

void CResistor::DisplayResistance(double, double, double, bool)
{
//your function code.
}

Does that go in the .h file or the .cpp?

[greenleaf800073]

void main() ?!?!?!!??!!? fix that please...

[Michaela Elise]

When you declare a CResistor you need to construct it with the parameters you gave it

No a .h file is separate from a .cpp file
in the .cpp file you need to

#include "CResistor.h" //or whatever you named it 

CResistor (double, double, string, bool);

so in main you need

CResistor resObj(double, double, string, bool); //Replace types with the initial values you want 

p.s. and please use

int main()
{
......
.....
return 0;
}

[Yom]

The void main (void) was in there from my professor. What gets you so excited about it?

[Michaela Elise]

New convention. Windows will let you use void main, but unix/linux will not. So int main() works in both.

I am not really that excited though. There are much more exciting things in life :)

[Yom]

Alright so I went from what I thought was a rudamentry understanding to confusion. I can't declare " resObj " as an object? Like int x or in this case " CResistor resObj; ". I must declare it as a function; am I understanding this correctly?

[Michaela Elise]

no, you are declaring it as an object, but your object has a constructor that takes parameters.

so the way you currently have it declared
CResistor resOBJ(3.4, 2.7, "poop, 1);

resObj is a type just like x in int x.

if you do not want to initialize it with parameters then your constructor (in your class) should just be
CResistor(); //Add this to your class to allow a CResistor object that takes no parameters to construct

The way you have res1, res2, res3 are declared properly

[Michaela Elise]

I noticed you have void resObj (double, bool); in your class.

when you declare a CResistor object then you can call something like res1.resObj(param1, param2);

resObj is a function in your class

[Michaela Elise]

Ok sorry, I now noticed what your misunderstanding is

http://www.cplusplus.com/doc/tutorial/classes/

go there and start from scratch with classes. After a little practice with some simple stuff you should get it no problem.

[Dante12129]

Another piece of advice: don't use any namespaces in a header, as this forces anything using the header to use that namespace.

[Martaoem]

Thanks to all of you.... i need this type of information... :)

[BinaryGeek]

void CResistor::DisplayResistance(double, double, double, bool)
{
//your function code.
}

will go in a separate cpp file, so you'll have 3 files total: a header, implementation, and main. Why 3 instead of just 1 file? Cause the code can/will get big and its better readability.

[Yom]

I finally figured out the answer to my question. There are two kinds of constructors, default Constructor::Constructor {} and a constructor with parameters Constructor::Constructor (int, double, bool, ...... ect {}

The default will have a single object like Constructor Tom;
The other will have a single object with one or more parameters like Constructor Yom (double, int);