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[news.eclipse.modeling.mdt.ocl] Re: New to EMF and OCL - Question: If my method returns void, how do I use it in the invariant? 
Hi Richard

Any OCL expression is side effect free, so anything used in an OCL invariant is side effect free, so why would you want to call a method that returned void? the method returns nothing and so does nothing.

So the answer is you can't.

NB. Your inv_4 is a comparison not an assignment.

NB. Your inv-5 invokes a side effecting function and so is not a valid OCL invariant.

	Regards

		Ed Willink

Richard Catlin wrote: 
Ed,

Thanks. I ordered Kleppe's book. I was reading Ch 7 of the OCL Spec, and did understand the syntax. The problem I was having was understanding how to call a method on the generated code; mainly because I was using the OCL text file to create the invariants. I finally got this method to work:

    public boolean setOutput1() {
        setHardwareNotes("test33");
        return true;
    }

with the invariant declared as:

package sizing

context Architecture

inv inv_3: self.questions->size() < 1

inv inv_4: self.hardwareNotes = 'hw5'

inv inv_5: self.setOutput1()

endpackage

Question:  If my method returns void, how do I use it in the invariant?

Regards,
Richard Catlin



On 8/6/2009 9:50 PM, Ed Willink wrote: 
HI Richard

I am sorry, but if you want help learning the OCL lanaguage you should consult one of the inline guides or buy a book. I found that Warmer and Kleppe's book is very readable.

    Regards

        Ed Willink

Richard Catlin wrote: 
Ed,

I'm not sure where I should use
self.hardwareNotes = 'hw1'

I am using the OCL text file, so should it be something like this?

package sizing

context: Architecture
if(true)
    self.hardwareNotes = 'hw1'
end

endpackage

Thank you for your help.

Regards,
Richard Catlin


On 8/6/2009 12:26 PM, Ed Willink wrote: 
Hi Richard

setHardwareNotes is an implementation artefact created by EMF, it is not part of the Ecore class, so it is not accessible from OCL, although the OCL implementation may use it.

You have defined a property so that is what you should use.

    self.hardwareNotes = 'hw1'

   Regards
        Ed Willink


Richard Catlin wrote: 
Further thoughts on this question:

If I create a simple EClass called Architecture in Ecore with a property of "hardwareNotes", then when I generate the model, a setHardwareNotes(String name) method is generated. When I use the Interactive OCL Console, I get the following error:

self.setHardwareNotes('hw1')

Cannot find operation (setHardwareNotes(String)) for the type (Architecture)

How can I go about setting this?

Thank you,
Richard

On 8/4/2009 8:13 PM, Richard Catlin wrote: 
All,

I am using the EMF Framework Validation Plug-in: "OCL Example". It allows me to write OCL expressions in a text file.

Is it possible to set properties in the model based on OCL expressions? The OCL 2.0 Spec says that expressions are guaranteed to be without side effects, but then goes on to say that OCL expressio can be used to specify a state change (eg. in a post-condition).

Pardon me if this is an obvious question.  I am new to EMF and OCL.

Thank you,
Richard Catlin