static constructors and destructors in C++

Nish Nishant

[removed]

Tim Smith

A static constructor without a this? What would you be constructing? Tim Smith Descartes Systems Sciences, Inc.

Tim Smith

Ah, I see. What people have done in the past is create a class whos member variable is the variable to be initialized at program start. Then just create one global instance of that class. Tim Smith Descartes Systems Sciences, Inc.

Nish Nishant

[removed]

Tim Smith

DOH, stupid me. Create any class and create a global instance of it. Use that to perform any program start initializations. Tim Smith Descartes Systems Sciences, Inc.

Michael Dunn

There is no such thing. You'd do something like:

// In foo.h:
class C
{
public:
static int m_stat_var;
static int stat_func() { return 1; }
};

// In foo.cpp:
int C::m_stat_var = C::stat_func();

--Mike-- "There are only a limited number of jobs where they will ask to see the sausage. Most of them are in movies." -- Christian Graus, 2/11/2002 My really out-of-date homepage Sonork - 100.10414 AcidHelm Big fan of Alyson Hannigan.

Atul Dharne

Static Constructor...The idea is kinda weird :-)..How are they implemented in C#? Atul Sonork 100.13714 netdiva

Nish Nishant

[removed]

Michael Dunn

That's Just The Way It's Done. :) It's similar to the situation when you write "extern int n;" in a header file. You still need to actually declare the variable "int n;" in a .cpp file. --Mike-- "There are only a limited number of jobs where they will ask to see the sausage. Most of them are in movies." -- Christian Graus, 2/11/2002 My really out-of-date homepage Sonork - 100.10414 AcidHelm Big fan of Alyson Hannigan.

Nish Nishant

[removed]

Michael Dunn

Well, I can't really answer that since I don't know C#, so don't know what you mean by a static constructor. :( --Mike-- "There are only a limited number of jobs where they will ask to see the sausage. Most of them are in movies." -- Christian Graus, 2/11/2002 My really out-of-date homepage Sonork - 100.10414 AcidHelm Big fan of Alyson Hannigan.

Ravi Bhavnani

Looks like a factory pattern is what you want. /ravi "There is always one more bug..." http://www.ravib.com ravib@ravib.com

Nish Nishant

[removed]

Ravi Bhavnani

One use of a factory design pattern is to ensure that objects are properly initialized during construction. I assume this is what you'd like to accomplish via the static constructor. To implement a factory pattern for the class CFoo, do the following:

Make CFoo's constructor protected, thereby preventing anyone from doing CFoo* pFoo = new CFoo(); which could create an uninitialized instance.
Implement the static method CFoo* CFoo::Create(); that serves up a properly initialized object. The static method can set the class's static member is required.

You should browse thru the gang of 4 book. I think you'll enjoy it. /ravi "There is always one more bug..." http://www.ravib.com ravib@ravib.com

Ravi Bhavnani

Nish [BusterBoy] wrote: Why am I re-declaring the static int You're not redeclaring it. The .h file declares it - the .cpp allocates storage for it. If you omitted it from the .cpp file you'd get an unresolved reference link error. /ravi "There is always one more bug..." http://www.ravib.com ravib@ravib.com

Atul Dharne

You are not redeclaring it but you are just declaring it. As it is static it resides even if your class object has not been constructed. It is like using static variables in functions or global vars. IMO the compiler initialises them to zero if you don't do the essentials. So here just after your class def you should initialize it otherwise the compiler spews errors. Atul Sonork 100.13714 netdiva

Nish Nishant

Ravi Bhavnani wrote: If you omitted it from the .cpp file you'd get an unresolved reference link error. Yes I did get that error :-O :-O :-O or if you want it in Ravi-talk pinky pinky :-) Nish Nish was here, now Nish has gone; He left his soul, to turn you on; Those who knew Nish, knew him well; Those who didn't, can go to hell. I like to :jig: on the Code Project Sonork ID 100.9786 voidmain www.busterboy.org

Ravi Bhavnani

I think I said "picky picky". :) /ravi "There is always one more bug..." http://www.ravib.com ravib@ravib.com

Navier

Seems to me like a Singleton pattern would do the job better. BTW the standard (well Nov96 draft at least) says a constructor can't have a static modifier (12.1 para 4) if you want official confirmation. i1.2sqrt(u).bcos(ur)sec(c) but b4.isqrt(u).ru/16

Ravi Bhavnani

I think the Singleton pattern is better suited when you want to expose methods from the one and only instance of a class. But I agree that the ClassFactory pattern can do more than serve up a single class. In fact, it's power lies in the fact that it can serve up specializations of a general base class. /ravi "There is always one more bug..." http://www.ravib.com ravib@ravib.com