Pointers, Classes, and Errors o my!

Ok heres my class under header files as P1.h:


typedef unsigned long int ULONG;

class P1;
{
public:
ULONG* pointer;
pointer=&h;
private:
ULONG h, m, s;
return 0;
}

Now heres main.cpp:

#include <iostream.h>
#include "p1.h"

int main()
{
P1 test;
test.pointer = 100;
cout << "test.pointer = " << test.pointer;
return 0;
}

Now heres the annoying errors I get:

--------------------Configuration: PointerNClass - Win32 Debug--------------------
Compiling...
main.cpp
c:\program files\microsoft visual studio\myprojects\pointernclass\p1.h(5) : error C2447: missing function header (old-style formal list?)
c:\program files\microsoft visual studio\myprojects\pointernclass\main.cpp(6) : error C2079: 'test' uses undefined class 'P1'
c:\program files\microsoft visual studio\myprojects\pointernclass\main.cpp(7) : error C2228: left of '.pointer' must have class/struct/union type
c:\program files\microsoft visual studio\myprojects\pointernclass\main.cpp(8) : error C2228: left of '.pointer' must have class/struct/union type
Error executing cl.exe.

PointerNClass.exe - 4 error(s), 0 warning(s)


I am trying to learn pointers and classes. They are hard to understand and I cant figure this one out.

missing semicolon at end of class declaration.

PS.

Didnt your mother tell you not to play with your privates in public?! :confused: :D

Lol

btw void main is also undefined behaviour.... use int main instead and return something back to the os at the end of main commonly 0 is returned.

Guess you shouldn´t be making statements in class declaration:

Code:

---

pointer=&h;

---

Do this in your constructor instead!

I dont understand constructor/destructors.

nope dont need those () after P1 either

its simple a constructor is called to make an object and a destructor is called to destroy an object.

your class...

Code:

---

class P1
{
public:
    typedef unsigned long ULONG;
    P1() : h(0),m(0),s(0) {} // constructor. syntax looks daunting
    P1( ULONG H,ULONG M,ULONG S)
        {
            h = H;
            m=( M > 59 )? 59 : M ;
            s = (S > 59 ) ? 59:S;
        }
    P1( const P1& rhs ) : h(rhs.h),m(rhs.m),s(rhs.s) {}
    ~P1() {} // the do nothing destructor
private:
    ULONG h, m, s;
};

---

Notice we have three constructors.
the first allows us to do this....

Code:

---

P1 myp1;

---

Its called a default constructor.
The next allows us to do this...

Code:

---

P1 myp1 (10,10,10);

---

constructing from ULONG,ULONG,ULONG
the last one is called the copy constructor. This constructs from another P1 object.

Code:

---

P1 a;
P1 b(a);

---

The destructor does othing in this example as there are no resources to be freed. Destructors get heavier use when you deal with dynamic memory.

class p1
{ ...
return 0; // ???
};

int main()
{
// do stuff here
return 0;
}

This should work...although its not using the header file like you want.

Code:

---

#include <iostream.h>

typedef unsigned long ULONG;

class P1{
public:
ULONG* pointer;
P1() { pointer = &h; }  // constructor
display();
private:
ULONG h, m, s;
};

int main()  //always use int main ( )
{
P1 *test;          // Make it a pointer so you can allocate dynamic memory
test = new P1; // You must allocate memory

// the value of the pointer should be = 100

*test->pointer = 10; 

cout << "test.pointer = ";

test->display();

return 0;  // always return a value
}

P1::display()
{
        cout << *pointer << endl;
}

---

you should delete at the end too

delete test;