• nail <nail_member pathlink.com> Nov 19 2004
• J C Calvarese <jcc7 cox.net> Nov 19 2004

nail <nail_member pathlink.com> writes:

I tried to make a singleton for some particular class. As in C++ I made
constructor of this class protected, made method for instance access and so on.
All works fine until I try to instanciate my class outside the module where it
is defined. I was surprised but I didn't get any compile error after this trick.
How to prevent construction of class outside any module other then class owner?

Kernel kernel;

static this()
{
kernel = new Kernel;
}

class Kernel
{
protected:
this()
{
hInstance = GetModuleHandleA(null);
}
public: 
.....
}

// another module snipet

int main ( char [] [] args )
{
Kernel k = new Kernel; // no error!

kernel.runMainLoop();

return 0;	
}

Is it normaly?

----
nail

J C Calvarese <jcc7 cox.net> writes:

nail wrote:
 I tried to make a singleton for some particular class. As in C++ I made
 constructor of this class protected, made method for instance access and so on.
 All works fine until I try to instanciate my class outside the module where it
 is defined. I was surprised but I didn't get any compile error after this
trick.
 How to prevent construction of class outside any module other then class owner?


I think you're pretty close to your goal. Most importantly, you probably 
should upgrade to DMD 0.106. A recent bugfix allows privatizing this().

The following code works for me (i.e., it doesn't)...



/* *** kernel.d *** */

import std.c.windows.windows;

Kernel myKernel;

static this()
{
     myKernel = new Kernel;
}


class Kernel
{

protected:
this()
{
     void* hInstance = GetModuleHandleA(null);
}

public:
     void runMainLoop() {}
}



/* *** main.d *** */

import kernel;

int main ( char [] [] args )
{
     Kernel k = new Kernel; /* it won't work in DMD 0.106 */
     myKernel.runMainLoop();
     return 0;
}



 rem /* *** build.bat *** */
 echo off
dmd
dmd main.d kernel.d
main.exe
pause
erase *.obj
erase *.map


-- 
Justin (a/k/a jcc7)
http://jcc_7.tripod.com/d/