Destructors and Constructors on classes

Hi.
I have a C++ book right in front of me here, and it suggest making a destructor like this:

Code:

class SomeClass {
public:
~SomeClass ();  // Destructor definition
};


SomeClass::~SomeClass () {

}

But when i do this, exactly like the book says, i get this one:

Code:

  multiple definition of `SomeClass::~SomeClass()' 
  first defined here 
  ld returned 1 exit status 
  Makefile.win 
 [Build Error]  [YAPI.exe] Error 1

Looks like it doesent allow me to first define it, and then implement it...
Is it that this isnt, allowed, and that my C++ book is wrong?

Or is it a syntax error somewhere?

If you copied this verbatim from the book, then you've got a bad book.

The comment that says "destructor definition" is wrong. This line is the destructor declaration. The definition is further down, the SomeClass::~SomeClass thing.

The definition must go into a source file, not a header file. For example, you might have created a pair of files for SomeClass, like SomeClass.h and SomeClass.cpp. The destructor definition goes into SomeClass.cpp, while the class definition (including the destructor declaration) goes into SomeClass.h.

Okay, i have now remade my example:

SomeClass.h

Code:

class SomeClass {
public:
~SomeClass (); 
};

SomeClass.cpp

Code:

SomeClass::~SomeClass () {

}

I still get the same error... ideas?

You do not have to put the code in two seperate files for it to work..

I often write both my class specification and definition in the .h to make writing easier and then move the definition part to a separate .cpp later.
As for your error I do not know... thats how I would write it..

perhaps you should add a constructor implicitly...
Someclass();
~Someclass();

Though I doubt that is the problem..

You still get the same error? Hmm...

Are you #include'ing the .cpp file anywhere?

No, im not including the .cpp file anywhere..
(but i include the .h file in hte .cpp file, but thats self-explanatory...)


Could it be my compiler?
(Dev C++ 4.9.9.2?)

No, but perhaps your compilation process. Have you recompiled every .cpp file that included the .h file?

The definition must go into a source file

It should go into a source file, but it doesn't have to. It can be defined inline in the header (has some uses though not many).

Code:

Someclass::Someclass()
{
    ~Someclass();
}

Quzah.

still doesent work..
While THIS works:

Code:

class SomeClass {
public:
~SomeClass () {
//and here I go, as long as i make EVERYTHING within the declaration
}


};

Atleast, then the compiler shuts up and let me compile...
But im a man of principles, and this is a ugly and uncorrect way to do it! d:

What lines does the error message point at? It says "first defined here", where is here?

Make sure you don't have

Code:

~SomeClass() { }

instead of

Code:

~SomeClass();

as the declaration.

Also, though I dont think this is what you have, in your implementation make sure you dont have:

Code:

~SomeClass(); { }

The semicolon would make it appear as another definition.

Umm....I use Dev-C++ as well, and the code you posted in your very first post compiles and runs fine for me. Your book was correct. Your error is somewhere else. If you get a multiple definition error, then that's just what it is. You've probably #included the .h file more than once, therefore, it is defined/declared more than once. Here's what I have.

main.cpp

Code:

#include <cstdlib>
#include <iostream>

using namespace std;

#include "class.h"

int main(int argc, char *argv[])
 {
  system("PAUSE");
  return EXIT_SUCCESS;
 }

class.h

Code:

class SomeClass
 {
  public:
    ~SomeClass();  // Destructor declaration
 };

SomeClass::~SomeClass()
 {

 }

... I manually deleted all makefiles, objectfiles and various project-builds, restarted my computer, and clicked "rebuild all", and it finaly worked !

Heh. Dev-C++ is wierd, At least you got it working.