Re: Singleton Pattern
On Apr 19, 9:40 pm, "AnonMail2...@gmail.com" <AnonMail2...@gmail.com>
wrote:
On Apr 19, 9:07 am, Keshav <gupta.kes...@gmail.com> wrote:
[...]
//CODE SNIPPET
class Sing
{
public:
static Sing* Instance();
protected:
Sing(){}
~Sing(){}
private:
Sing(const Sing&);
Sing& operator= (const Sing&);
static Sing* pinstance;
};
Sing* Sing::pinstance = Instance(); // Please NOTE THIS.
pInstance is initialized at definition.
Sing* Sing::Instance ()
{
if (pinstance == 0)
pinstance = new Sing;
return pinstance;
}
I assume your code post is actually the .h and the .cpp file.
Or the entire project is just one big .cc file:-).
You could initialize pinstance as you did if you make
pinstance a non-pointer.
I'm not sure I follow. His solution requires pInstance to be a
pointer.
But then you need to consider two issues:
1. You are creating this object even if it is never used.
That's a possible consideration. (Most of the time, I suspect
that it doesn't matter.)
2. If another singleton uses this singleton, you run into
order of initialization issues. There is no guarentee that
the singleton that is needed is created before the one that
needs it if there are defined in separate compilation units.
By creating the objects on demand, you don't have these
issues.
He is creating the object on demand. He's just forcing a demand
during dynamic initialization.
--
James Kanze (GABI Software) email:james.kanze@gmail.com
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