C++ Classes

Linkdude

I'm having trouble making classes with C++. I keep removing this, putting in that and the errors come up and down. Some times, when I compile the exact same thing twice, I get a different number of errors.

Here:

#include <iostream.h>
#include <stdlib.h>


class Person;
 {
  unsigned int IQ;
  unsigned int Weight;
  unsigned int Age;
 }

int main()
{
  Person Alan;
  Person Jonny;
  Alan.IQ = 104;
  Alan.Weight = 116;
  Alan.Age = 32;
  Jonny.IQ = 110;
  Jonny.Weight = 128;
  Jonny.Age = 39;
  cout << "Alan's IQ is " << Alan.IQ << " while Jonny's IQ is " << Jonny.IQ << ".\n";
  cout << "Alan's weight is " << Alan.Weight << " Pounds, while Jonny's Weight is " << Jonny.Weight << ".\n";
  cout << "Alan is " << Alan.Age << "while Jonny is " << Jonny.Age << ".\n";
  system("PAUSE");
  return 0;
}

I get errors here:

Parse errors before '{' and '}'

class Person;[i] //For some reason, by putting in a semicolon, I get less errors[/i]
 {
  unsigned int IQ;
  unsigned int Weight;
  unsigned int Age; 
 } [i]//I don't understand the parse errors stuff =/[/i]

I get errors here because the class is incomplete:

Person Alan;
  Person Jonny;

Thanks in advance.

projectmayhem

class X
{
public:

private:

};

is the usual way of doing things. i'm no c++ expert though so i may be leading you astray

nobodythere

I don't know much about classes but first of all take that semicolon out.

Secondly AFAIK classes do need that whole public/private thing. You might be confusing 'struct' and 'class'. If you changed the class thing to something like:

struct Person
{
  unsigned int IQ;
  unsigned int Weight;
  unsigned int Age;
}

Also as I said I know little about classes but I think you have to use the "New" operator to declare one.

I dunno, sorry if this isn't helpful

Linkdude

It turns out it did require public to be used, something I didn't know because the tutorial didn't tell me, I'm not using that again.

I don't know much about classes but first of all take that semicolon out.

The compiler kept telling me a semicolon was expected after Person. I took it out now, of course.

Thanks for the help!

i_am_dogboy

grasshopa wrote:

Also as I said I know little about classes but I think you have to use the "New" operator to declare one.

You don't have to use the new operator, declaring them as Linkdude did creates the objects on the stack, using the new operator creates the object on the heap.

Chris P Duck

class Person
{
unsigned int IQ;
unsigned int Weight;
unsigned int Age;

Person(){}; // constructor
~Person(){}; // destructor
}

projectmayhem

grasshopa wrote:

I don't know much about classes but first of all take that semicolon out.

you need that semicolon actually

proof: http://www.cs.wisc.edu/~hasti/cs368/CppTutorial/NOTES/CLASSES-INTRO.html

boyracer87

I think you need the semicolon after the curly brackets and not after "Person" and change to struct:

struct Person
{
unsigned int IQ;
unsigned int Weight;
unsigned int Age;
};