Re: Use of static keyword instead of global object
On Feb 12, 9:16 pm, Dave Rahardja
<drahardja_atsign_pobox_dot_...@pobox.com> wrote:
On 12 Feb 2007 16:54:54 -0800, "Sam.Gun...@gmail.com" <Sam.Gun...@gmail.com>
wrote:
Hi,
I wish to share an object through a bunch of functions without
declaring it globally. I have achieved this through the following
function:
VideoReceiver* getReceiver()
{
static VideoReceiver *vr = new VideoReceiver();
return vr;
}
So, the first time it is called a new VideoReceiver object is created.
Subsequent calls return this object (without creating new ones).
E.g, All one needs to do to access the VideoReceiver is:
function blah()
{
VideoReceiver vr = getReceiver();
vr->update()
//do blah
}
Are there any problems or issues I should be aware of using this type
of code? Is it a no-no? I make multiple calls to getReceiver() each
frame.
It was originally a hack to get going but now that I've advanced a
reasonable way I'm considering just leaving it, since it is currently
working as expected.
Thanks for any advice or suggestions,
Sam.
There is no problem with this kind of code, except that the VideoReceiver
object is never destroyed.
Your solution is actually a common implementation of the Singleton pattern in
C++. A more typical code would be:
MyClass& getClassInstance()
{
MyClass myClass;
return myClass;
}
The pattern you are using also solves a common problems with globals:
initialization order.
-dr
Like dr says, this is the singleton pattern and is quite useful. I
find it useful to use a singleton as a non-copyable as well like so:
class Singleton
{
public:
virtual ~Singleton() {}
protected:
Singleton() {}
Singleton( const Singleton& singleton ) {}
Singleton&
operator=( const Singleton& singleton ) {}
} ;
class MyClass : public Singleton
{
public:
static MyClass&
Instance()
{
if( !_instance )
{
boost::shared_ptr< MyClass > temp( new MyClass() ) ;
_instance = temp ;
}
return _instnace ;
}
void
foo() ;
private:
static boost::shared_ptr< MyClass > _instance ;
} ;
And then you can just do:
MyClass::Instance().foo() ;
or
MyClass& inst = MyClass::Instance() ;
inst.foo() ;
To use it in code.
HTH,
Paul Davis