| [QVTO] Avoiding multiple object creation [message #91769] |
Wed, 08 October 2008 15:37  |
Eclipse User |
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Originally posted by: mahdider.students.uni-mainz.de
Hello,
I have the following code for creating a mutator for each attribute:
/*
Generates a mutator or setter method for a given attribute.
*/
mapping SIMPLE_UML::UmlAttribute::attribute2Setter() :
SIMPLE_UML::UmlMethod {
name := 'set' + self.name.firstToUpper();
visibility := UmlVisibility::PUBLIC;
-- TODO add parameters.
-- Create a new object, since void is unknown in the incoming model.
classifier := object UmlClassifier {
name := 'void';
};
}
The issue is of course, that this method is being called multiple times
and this will result in multiple "void" classifier instances in the
target model. I played around with var, basically trying to keep a
reference to the created object but it did not really work (syntax wise)
as I expected.
What is a good way to create such instances only once? Or should I
basically check somehow if there is already such an instance in self.
with some resolve() call) and then create the instance only?
Thanks for your help!
Best Regards,
Mahdi D-Manesh
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| Re: [QVTO] Avoiding multiple object creation [message #91783 is a reply to message #91769] |
Wed, 08 October 2008 16:16  |
 Radomil Dvorak
Messages: 249
Registered: July 2009 |
Senior Member |
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Hi Mahdi,
The easiest way to define a singleton is using mapping with no input =
parameters.
If such a mapping is executed, a trace for the mapping call with empty s=
et =
of source
objects is recorded.
Any subsequent call represents a call on the same source objects (empty =
=
set) and
the result is fetched from traces instead of executing the mapping again=
..
See the example bellow:
main() {
var x :=3D map singleVoid();
var y :=3D map singleVoid();
assert fatal (x =3D y);
}
mapping singleVoid() : UML::Classifier {
name :=3D 'void';
}
Another technique could be to check for existing instances in the init {=
} =
section and
eventually assign one of them to the 'result' variable explicitly, thus =
=
limiting a repeated creation.
This might be useful, if you have specific constraints on the number of =
=
instances
to be created. The former way is the simplest for your usecase.
Regards,
/Radek
On Wed, 08 Oct 2008 17:37:26 +0200, Mahdi D-Manesh =
<mahdider@students.uni-mainz.de> wrote:
> Hello,
>
> I have the following code for creating a mutator for each attribute:
>
> /*
> Generates a mutator or setter method for a given attribute.
> */
> mapping SIMPLE_UML::UmlAttribute::attribute2Setter() : =
> SIMPLE_UML::UmlMethod {
> name :=3D 'set' + self.name.firstToUpper();
> visibility :=3D UmlVisibility::PUBLIC;
> =
> -- TODO add parameters.
>
> -- Create a new object, since void is unknown in the incoming model.
> classifier :=3D object UmlClassifier {
> name :=3D 'void';
> };
> }
>
> The issue is of course, that this method is being called multiple time=
s =
> and this will result in multiple "void" classifier instances in the =
> target model. I played around with var, basically trying to keep a =
> reference to the created object but it did not really work (syntax wis=
e) =
> as I expected.
>
> What is a good way to create such instances only once? Or should I =
> basically check somehow if there is already such an instance in self. =
=
> with some resolve() call) and then create the instance only?
>
> Thanks for your help!
>
> Best Regards,
> Mahdi D-Manesh
-- =
Using Opera's revolutionary e-mail client: http://www.opera.com/mail/
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| Re: [QVTO] Avoiding multiple object creation [message #91867 is a reply to message #91783] |
Thu, 09 October 2008 09:25 |
| Eclipse User |
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Originally posted by: mahdider.students.uni-mainz.de
Radek,
I tried your approach and it works like expected. So I am using the
"singleton" way now. :)
Best Regards,
Mahdi
Radek Dvorak schrieb:
> Hi Mahdi,
>
> The easiest way to define a singleton is using mapping with no input
> parameters.
> If such a mapping is executed, a trace for the mapping call with empty
> set of source
> objects is recorded.
> Any subsequent call represents a call on the same source objects (empty
> set) and
> the result is fetched from traces instead of executing the mapping again.
>
> See the example bellow:
>
> main() {
> var x := map singleVoid();
> var y := map singleVoid();
> assert fatal (x = y);
> }
>
> mapping singleVoid() : UML::Classifier {
> name := 'void';
> }
>
>
> Another technique could be to check for existing instances in the init
> {} section and
> eventually assign one of them to the 'result' variable explicitly, thus
> limiting a repeated creation.
> This might be useful, if you have specific constraints on the number of
> instances
> to be created. The former way is the simplest for your usecase.
>
> Regards,
> /Radek
>
>
>
> On Wed, 08 Oct 2008 17:37:26 +0200, Mahdi D-Manesh
> <mahdider@students.uni-mainz.de> wrote:
>
>> Hello,
>>
>> I have the following code for creating a mutator for each attribute:
>>
>> /*
>> Generates a mutator or setter method for a given attribute.
>> */
>> mapping SIMPLE_UML::UmlAttribute::attribute2Setter() :
>> SIMPLE_UML::UmlMethod {
>> name := 'set' + self.name.firstToUpper();
>> visibility := UmlVisibility::PUBLIC;
>>
>> -- TODO add parameters.
>>
>> -- Create a new object, since void is unknown in the incoming model.
>> classifier := object UmlClassifier {
>> name := 'void';
>> };
>> }
>>
>> The issue is of course, that this method is being called multiple
>> times and this will result in multiple "void" classifier instances in
>> the target model. I played around with var, basically trying to keep a
>> reference to the created object but it did not really work (syntax
>> wise) as I expected.
>>
>> What is a good way to create such instances only once? Or should I
>> basically check somehow if there is already such an instance in self.
>> with some resolve() call) and then create the instance only?
>>
>> Thanks for your help!
>>
>> Best Regards,
>> Mahdi D-Manesh
>
>
>
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