singleton pattern, return sole pt per reference

[Chris Forone]

its ok to return *this as reference (C++ FAQ L).

but is it also in singleton pattern (ctor example below)?

Timer* Timer::sole(0); // static

Timer& Timer::Get() // static
{
return sole ? *sole : *(sole = new Timer);
}

i think it isnt only if using new (std::nothrow),because of exeption
handling!?

HAND, Chris

 

[Frank Birbacher]

Hi!

its ok to return *this as reference (C++ FAQ L).
Yes.

but is it also in singleton pattern (ctor example below)?

Yes. Whenever you get a "this" you may return it.

Timer* Timer::sole(0); // static

Timer& Timer::Get() // static
{
return sole ? *sole : *(sole = new Timer);
}

I don't see any "this*" here. And "static" functions do not have a
"this" pointer, anyway. Your code is fine but I don't understand your
question here.

Frank

 

[Chris Forone]

Hi!



Yes. Whenever you get a "this" you may return it.


I don't see any "this*" here. And "static" functions do not have a
"this" pointer, anyway.

yes, but it returns a reference from a pointer. and if i use "new
(std::nothrow)" it returns a reference from a 0-pointer (bad in C++ FAQ L)

Your code is fine but I don't understand your

question here.

if the code is fine, no more question...

Frank

thanks a lot, chris

 

[Frank Birbacher]

Hi!

yes, but it returns a reference from a pointer. and if i use "new
(std::nothrow)" it returns a reference from a 0-pointer (bad in C++ FAQ L)

Yeah, right. Bad bad. Hmm, but you could reserve memory in advance:

#include <boost/type_traits.hpp>
using namespace boost;

Foo& getInstance()
{
//use static POD
static bool initialized = false;
static aligned_storage<sizeof(Foo), alignment_of<Foo>
::value> storage;

if(!initialized)
{
//construct Foo in storage
new (&storage) Foo();
initialized = true;
}

//return instance from storage
return *reinterpret_cast<Foo*>(&storage);
}

HTH,
Frank