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How to increment an id feature automatically [message #1786549]

Mon, 07 May 2018 03:29

Eclipse User

Hi folks,

I would like to know if it is possible to set an id feature of an object with 1 when the user creates it the first time. Then, other objects of the same type would have that id automatically incremented.

How to do this?

Regards

Adalberto Jr

Re: How to increment an id feature automatically [message #1786551 is a reply to message #1786549]

Mon, 07 May 2018 04:00

Eclipse User

Hello,

In your set operation you can use an AQL expression that will count the number of element of the same kind that the one created. It will be something like in the basic family example aql:container.members->filter(basicfamily::Man)->size()

Regards

Re: How to increment an id feature automatically [message #1786556 is a reply to message #1786551]

Mon, 07 May 2018 04:26

Eclipse User

Hi

You need to answer questions such as:

does a derived class share/override the counter of the base class?

are stale ids re-used after deletion? i.e. if {1,2,3} are created, then 2 is deleted leaving {1.3} , what is the next id?
- 2 (fill the gap) => {1,2,3}
- 3 (count the elements, as in the AQL snippet) - oops => {1,3,3}
- 4 (next all-time) => {1,3,4}

are missing ids re-used after reloading? if I save a model one day and continue the next, loading {56,57,58}, is the next id 1 or 59?

does reloading reuse old IDs or start from 1?

are IDs reassigned by copy and paste?

You can elaborate the AQL to avoid re-use of ids, but what you require is a class level operation for which some variant of allInstances() and/or search is necessary; clumsy and inefficient; an interesting optimization challenge for tool vendors. If you really want to do this, I would recommend a Java/EMF solution in which getID() lazily allocates the ID from a 'static' EClass Map/Set appropriately scoped by derived EClasses. setID() will be invoked automatically by the loader if you choose to persist the ID. The transient and volatile attributes should support your design choice.

Regards

Ed Willink

Re: How to increment an id feature automatically [message #1786558 is a reply to message #1786556]

Mon, 07 May 2018 04:54

Eclipse User

Hi

"an interesting optimization challenge for tool vendors" ... https://bugs.eclipse.org/bugs/show_bug.cgi?id=534421 raised

The solution would be fairly easy if Ecore had 'static' modeling support like UML and OCL: https://bugs.eclipse.org/bugs/show_bug.cgi?id=285771

OCL may be able to workaround it, not a high priority, but thanks for an interesting motivating use case.

Regards

Ed Willink

Re: How to increment an id feature automatically [message #1786559 is a reply to message #1786551]

Mon, 07 May 2018 04:55

Eclipse User

Great.

Works fine.

Tks

Re: How to increment an id feature automatically [message #1786560 is a reply to message #1786559]

Mon, 07 May 2018 04:59

Eclipse User

Ed, I'll analyze your suggestions.

In fact, you are right.

Tks

Re: How to increment an id feature automatically [message #1786614 is a reply to message #1786560]

Tue, 08 May 2018 09:07

Eclipse User

Ed,

I was thinking about you said and I guess that it'd be enough to get the last ID used + 1.

It's not necessary to me fill gaps or reuse IDs.

So, as I'm new in Sirius, how can I do this? Calling Java services, functions?

Regards.

Re: How to increment an id feature automatically [message #1786618 is a reply to message #1786614]

Tue, 08 May 2018 09:49

Eclipse User

Hi

In AQL/OCL it's rather hard. In Java/EMF it's pretty easy; just define a static counter variable in the EClass Impl and bump it whenever getID() needs to create/allocate an ID. But make sure the attribute is derived, transient, !volatile, to ensure that loading/copying creates new IDs. Define distinct static counters in the EClass for each distinct ID-space, or just a single one in your 'ElementWithID' class from which every ID class derives.

private static int idCounter = 0;

public String My::getID() {
if (id == null) {
id = "My" + ++idCounter;
}
return id;
}

Regards

Ed Willink

Re: How to increment an id feature automatically [message #1786765 is a reply to message #1786618]

Thu, 10 May 2018 16:13

Eclipse User

Ed,

I created a method getID in the class Services.java but it's not available when I press ctrl + space (set operation - value expression).

Here's my class:

public class Services {

private static int idMU = 0;

/**
* See http://help.eclipse.org/neon/index.jsp?topic=%2Forg.eclipse.sirius.doc%2Fdoc%2Findex.html&cp=24 for documentation on how to write service methods.
*/
public EObject myService(EObject self, String arg) {
// TODO Auto-generated code
return self;
}

public Integer getID() {
//if (idMU == null) {
//idMU = ++idMU;
//}
return ++idMU;
}

}

[Updated on: Thu, 10 May 2018 16:14] by Moderator

Re: How to increment an id feature automatically [message #1786766 is a reply to message #1786765]

Thu, 10 May 2018 16:36

Eclipse User

Sorry,

I fixed the problem and the method ID appeared.

My last question is: if I save the model and quit the diagram, the var ID will return to 0. And this is an error.

So, it's necessary to make a for loop in each EObject and get the max ID saved.

Could you, please, give an idea how to do this?

Is there any AQL function the returns a max value of a feature?

Regards.

Re: How to increment an id feature automatically [message #1786768 is a reply to message #1786766]

Thu, 10 May 2018 17:17

Eclipse User

I made a service but when I reopen the Diagram, the value of ID returns to 0.

Any idea?

private static int idMU = 0;

/**
* See
* http://help.eclipse.org/neon/index.jsp?topic=%2Forg.eclipse.sirius.doc%2Fdoc%2Findex.html&cp=24
* for documentation on how to write service methods.
*/
public EObject myService(EObject self, String arg) {
// TODO Auto-generated code
return self;
}

public Integer getID(MU mu) {
ArrayList<MU> list = new ArrayList<MU>();
for (MU mu2 : list) {
if (idMU < mu2.getId()) idMU = mu2.getId();
}
return ++idMU;
}

Re: How to increment an id feature automatically [message #1786776 is a reply to message #1786768]

Fri, 11 May 2018 03:58

Eclipse User

hi

I wrote

"But make sure the attribute is derived, transient, !volatile, to ensure that loading/copying creates new IDs."

Regards

Ed Willink

Re: How to increment an id feature automatically [message #1786797 is a reply to message #1786776]

Fri, 11 May 2018 17:07

Eclipse User

Ed,

when I set up the ID feature as you suggested, I noticed the ID's returned to 0, for all objects.

I noticed too that IDs weren't available anymore to user edition in the properties window.

Look how I did.

Attachment: 1.png
(Size: 40.29KB, Downloaded 148 times)

Re: How to increment an id feature automatically [message #1786800 is a reply to message #1786797]

Sat, 12 May 2018 01:12

Eclipse User

Hi

Your original question was:

"I would like to know if it is possible to set an id feature of an object with 1 when the user creates it the first time. Then, other objects of the same type would have that id automatically incremented."

Of course it should not be edited since edits will not be saved; IDs are created lazily after loading. If you now want to allow editing you need to have a very clear plan for resolving clashes between new/copied/loaded/manually-re-used IDs.

I suggest you go back to the problem and work out what problem you are trying to solve. Then you may be able to formulate the requirements for your solution.

Regards

Ed Willink

Re: How to increment an id feature automatically [message #1786811 is a reply to message #1786800]

Sat, 12 May 2018 15:09

Eclipse User

Ok, Ed.

Please forgive me If my questions became a little bit confused. My goal has changed a bit because I'm evolving in using the tool.

Let me try to explain:

I did a Java service that returns the max ID used (below).

private static int idMU = 0;

/**
* See
* http://help.eclipse.org/neon/index.jsp?topic=%2Forg.eclipse.sirius.doc%2Fdoc%2Findex.html&cp=24
* for documentation on how to write service methods.
*/
public EObject myService(EObject self, String arg) {
// TODO Auto-generated code
return self;
}

public Integer getID(MU mu) {
ArrayList<MU> list = new ArrayList<MU>();
for (MU mu2 : list) {
if (idMU < mu2.getId()) idMU = mu2.getId();
}
return ++idMU;
}

It's good for my goals, but there's a problem (for this moment): If I save and quit the diagram with 3 nodes (max ID = 3) and open it again later, the service doesn't return the max ID = 3 anymore. If I create a node, the ID is set to 1, instead of 4.

In other words, if the user quit the diagram to continues to create nodes later, the IDs will repeat.

Re: How to increment an id feature automatically [message #1786812 is a reply to message #1786811]

Sat, 12 May 2018 15:41

Eclipse User

Hi

Yes. Very confused. and you don't make it any clearer. Obviously the solution for the old goal won't suit a changed goal. I have no idea what your goal is now. I suggest you review my earlier answer.

Do you want an auto-allocated ID that is guaranteed to exist and be unique, or do you want a persisted name with an initial hint that the user should improve, or .... ?

Until you know what properties you want ID to exhibit, it is very difficult to implement it.

(The IDs in your current solution do not repeat; they are ALL REALLOCATED starting at 0).

Regards

Ed Willink

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