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How to check derived or readonly with EBigDecimal types

medini_1066061996

Hi,

I've got an error message, when writing to an EBigDecimal member with following expression:

NewFailable.totalDistribution = oldFailable.totalDistribution;

The Java class "java.math.BigDecimal" has no public instance "readOnly".

How can I check this property without using try .. catch statement.?

Are there any ideas?

Thanks

Sincerly

Dieter

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medini_1024169437

Hello Dieter,

I assume you tried something like

if (NewFailable.totalDistribution.readOnly)

but that as you recognized wont work because that access readOnly on the value of the property, not the property itself (from metamodel perspective).

I see two options: you check Metamodel.package.class.attribute.derived for example Metamodel.safetyModel.Failable.totalDistribution.derived

But thats a static information which you also can get from the Metamodel, e.g. via the "What is this" Diagnostic view (attributes flagged with "*"):

Regards

Jan

medini_1059007410

Hi Dieter,

if you want to find out if a property is writable, then you can use the indications in the Element Attributes view (via Debug Mode > What is this?):

The "*" at the end indicates a read-only property. See also here for more details.

Identifying derived properties is possible also programmatically, but is a bit more complicated (via eClass attributes). Let me know if you really need that. I guess for normal cases checking the attributes view is normally sufficient.

Does that answer your question?

Regards,

Nils

PS: Jan was a bit faster ;-)

medini_1024169437

mid air collision :-)

medini_1066061996

Hi Nils, Hi Jan,

thanks for the fast response.

The "What is this" context menu is known for me in the meanwhile. And I assumed also, that the "*" indicates the read-only property.

According the error message "derived" or "read-only" I supposed that these properties can be dynamically changed. If it is changed during runtime the script fails. This is not user friendly.

Which object or class is able to write these members.

An EClass attribute description would be very helpful for me to avoid such internal exceptions.

Regards

Dieter

medini_1066061996

Hello Nils,

yes I need the eClass Attributes kowledge.

Thanks in advance.

Dieter

medini_1024169437

Hello Dieter,

I am not sure I understood your last comment. "Derived" simply means that the value of that property is not persisted with the models but instead computed using a certains cript or expression on request, basically when you read the property. That script or expression does not change of course during script execution and a script can change it either. The property of course may return different results based on what the scripts actually does and whether there were other changes. An example: the ASIL of a hazardous event is a derived proeprty and calculated based on E, S and C. It can be set actually but if your script changes either S, E or C, the value returned by ASIL is of course different. But the script behind ASIL doe snot change.

Does that help?

Jan

medini_1066061996

Hello Jan,

no. Now I'am confused. How many scripts are running simultaneously in your example?

Please see the error message in my first request. "(read-only or derived)". Derived is not the problem, if it meant the same attribute "derived" as "FailureRateCatalogsPackage.Literals.FR_VARIABLE" defined.

This "derived"-attribute is accessible for me, but not the attribute "read-only".

Regards

Dieter

medini_1059007410

Dieter,

Trying to reduce the confusion:

Properties in medini are either writable or read-only (not writable). So "read-only" is a characteristic/quality term, not a "property" itself.

Properties can be read-only (marked by "*" in the Element Attributes view), because we don't want them to be modified (very rare), or because they are computed from other inputs. Computed properties we call "derived" properties.

If a script reads from a derived property, then its logic is executed and thus the output computed from its inputs. It's not cached for script accesses. This isn't a parallel execution, but sequential (if the script requests the value, it has to wait until the derived property value has been computed).

If you want in your script check if the property is derived (and thus read-only), the you can check if ( Metamodel.safetyModel.Failable.totalDistribution.derived == true), as in Jan's first reply. Personally I think it is better to get that information manually from the Element Attributes view and just not try to write to the Property in your script.

Does that help?

Regards,

Nils

medini_1066061996

Hello Nils,

yes it helps,

Does this means, that all instances in the model of

Metamodel.safetyModel.Failable.scaled

Metamodel.safetyModel.Failable.scaling

Metamodel.safetyModel.Failable.totalDistribution

Metamodel.safetyModel.Failable.totalFailureRate

Metamodel.safetyModel.Failable.totalTransientFailureRate

Metamodel.safetyModel.Failable.integrityLevel

are allways derived?

Regards

Dieter

medini_1024169437

Ah, got it, thanks Nils. The original posts states it clearer as "derived attributes are marked with "*"." (so it does not say "read-only").

Jan

medini_1059007410

Hi Dieter,

yes, they are all derived and thus read-only.

Regards,

Nils