Re: [osg-users] singleton instane
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Hi Sajjadul,
On 13/10/2013 1:12, Sajjadul Islam wrote:
Thanks for the suggestion of the singleton design . I tried to design a
template base
class as follows :
Code: ... templateclass T class Singleton { public: /** * Init the actual
singleton. * Must be called BEFORE the class is used, like this: */ static
void
init() { assert( singletonClass_.get() == NULL); singletonClass_ = new T; }
/** * Get Pointer of the actual class * @return Pointer of the actual class
*/ static
T* getPtr() { assert( singletonClass_.get() != NULL); return
singletonClass_.release(); } ... But it crashes at the assertion. I tried
without
assertion , then debugger simply exits at the point where i call: ...
osgOpenCL::Context *cxt = osgOpenCL::SingletonosgOpenCL::Context::getPtr();
Did you call 'init' on the singleton class before this?
Also, the 'getPtr' is buggy, since it calls 'release' on the singleton object.
This
will work the first time round, but delete the object afterwards and will crash
on
subsequent calls.
Cheers,
/ulrich
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Re: [osg-users] singleton instane
Hi David,
Thanks for the suggestion of the singleton design . I tried to design a
template base class as follows :
Code:
namespace osgOpenCL
{
/**
This class helps to build the singleton design pattern.
Here you have full control over construction and deconstruction
of the object.
*/
templateclass T
class Singleton
{
public:
/**
* Init the actual singleton.
* Must be called BEFORE the class is used, like this:
*/
static void init()
{
assert( singletonClass_.get() == NULL);
singletonClass_ = new T;
}
/**
* Get Pointer of the actual class
* @return Pointer of the actual class
*/
static T* getPtr()
{
assert( singletonClass_.get() != NULL);
return singletonClass_.release();
}
/**
* Get reference of the actual class
* @return reference of the actual class
*/
static T getRef()
{
assert( singletonClass_.get() != NULL );
return *singletonClass_;
}
/**
* Has the actual class been inited?
*/
static bool isInited()
{
return (singletonClass_.valid());
}
private:
static osg::ref_ptrT singletonClass_;
};
/// init static pointers with 0
templateclass T
osg::ref_ptrT SingletonT::singletonClass_ = 0;
} // namespace
#endif // TGT_SINGLETON_H
But it crashes at the assertion. I tried without assertion , then debugger
simply exits at the point where i call:
Code:
//pull out the singleton context
//get the singleton context - which will be widely used in the rest of
this function definition
osgOpenCL::Context *cxt =
osgOpenCL::SingletonosgOpenCL::Context::getPtr();
Any idea how to get around these issues ?
Thanks,
Sajjadul
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[osg-users] singleton instane
Hello forum, I have a class declaration and i want to create a singleton instance to it. Is there any utility class inside OSG that enables something like this? Thank you! Cheers, Sajjadul -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=53820#53820 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] singleton instane
Hi Sajjadul, There isn't any general signleton template or base class in the OSG, but it's doesn't take much code to implement so when we use singleton's they tend to get implemented locally in the code via a static access method. Getting singleton's to work cross platform with thread safety on initialization can be a bit tricky though so sometimes you have to jump through hoops to get it to work in all instances. Robert. On 26 April 2013 09:53, Sajjadul Islam dosto.wa...@gmail.com wrote: Hello forum, I have a class declaration and i want to create a singleton instance to it. Is there any utility class inside OSG that enables something like this? Thank you! Cheers, Sajjadul -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=53820#53820 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] singleton instane
Hi Sajjadul,
There are nothing in OSG to do this, but make a class a singleton is really
straightforward.
- make constructor protected or private,
- add a static getInstance function
MyClass getInstance()
{
static MyClass * myClass = new MyClass();
return *myClass;
}
then use it in your code
MyClass::getInstance().doStuff();
alternatively, you can google 'boost+singleton' to see some examples of
implementation
HTH
David
2013/4/26 Sajjadul Islam dosto.wa...@gmail.com
Hello forum,
I have a class declaration and i want to create a singleton instance to it.
Is there any utility class inside OSG that enables something like this?
Thank you!
Cheers,
Sajjadul
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Re: [osg-users] singleton instane
oups beter like this, or with any other smart pointer
MyClass getInstance()
{
static osg::ref_ptrMyClass myClass( new MyClass() );
return *myClass;
}
2013/4/26 David Callu led...@gmail.com
Hi Sajjadul,
There are nothing in OSG to do this, but make a class a singleton is
really straightforward.
- make constructor protected or private,
- add a static getInstance function
MyClass getInstance()
{
static MyClass * myClass = new MyClass();
return *myClass;
}
then use it in your code
MyClass::getInstance().doStuff();
alternatively, you can google 'boost+singleton' to see some examples of
implementation
HTH
David
2013/4/26 Sajjadul Islam dosto.wa...@gmail.com
Hello forum,
I have a class declaration and i want to create a singleton instance to
it.
Is there any utility class inside OSG that enables something like this?
Thank you!
Cheers,
Sajjadul
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Read this topic online here:
http://forum.openscenegraph.org/viewtopic.php?p=53820#53820
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Re: [osg-users] singleton instane
On Fri, Apr 26, 2013 at 11:18 AM, David Callu led...@gmail.com wrote:
oups beter like this, or with any other smart pointer
MyClass getInstance()
{
static osg::ref_ptrMyClass myClass( new MyClass() );
return *myClass;
}
Do not forget to make all constructors private, though, otherwise you may
get a surprise when someone tries to construct your object using new
operator or define an STL vector of them ...
Regards,
Jan
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Re: [osg-users] singleton instane
On 04/26/2013 11:18 AM, David Callu wrote:
oups beter like this, or with any other smart pointer
MyClass getInstance()
{
static osg::ref_ptrMyClass myClass( new MyClass() );
return *myClass;
}
I wonder, why would you want a reference counting smart pointer for a
singleton? There will be only a single instance, no matter what you do,
so the smart pointer is useless.
Regards,
Jan
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Re: [osg-users] singleton instane
Hi Jan,
This is not for reference counting but to not forget to delete the instance
when program end.
Regards
David
2013/4/26 Jan Ciger jan.ci...@gmail.com
On 04/26/2013 11:18 AM, David Callu wrote:
oups beter like this, or with any other smart pointer
MyClass getInstance()
{
static osg::ref_ptrMyClass myClass( new MyClass() );
return *myClass;
}
I wonder, why would you want a reference counting smart pointer for a
singleton? There will be only a single instance, no matter what you do, so
the smart pointer is useless.
Regards,
Jan
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