Re: [e4-dev] Improved handling of ID's - Suggestion for discussion

[Lars Vogel <lars.vogel@xxxxxxxxxxxxxx>]

Hello Brian & Tom,

thanks for the clarification, that is exactly my suggestion. Managing ID's twice is one of the major pain points in Eclipse development and it would be great if we allow such an approach.

I will open a bug report for this feature, as this would be additional as you described I don't think its critical but it might be something to look at for Eclpise 4.3.

Thanks for the feedback, Lars

2012/1/31 Brian de Alwis <briandealwis@xxxxxxxxx>

I think an example of what Lars is talking about is to allow referencing an identifier from within a .e4xmi file that is actually defined in source code.  This would allow single-sourcing of an identifier.

For example, say we have a command defined for org.eclipse.ui.exit, and some code that wants to programmatically execute this command.  Currently we'd define the command in an e4xmi file:

       <commands elementId="org.eclipse.ui.exit" />

And then also reference the command identifier from a source file:

       public class MyPart {
               public static final String EXIT_ID = "org.eclipse.ui.exit";

               // does this work?
               @Inject @Named(EXIT_ID) MCommand exitCommand;
               @Inject EHandlerService hs;

               public void executeExit() {
                       hs.executeHandler(new ParameterizedCommand(exitCommand, null));
               }
       }

Currently, org.eclipse.ui.exit has to be used both in the .e4xmi file defining the command, and in the code.

Lars' suggestion would change the e4xmi to something like:

       <commands elementId="model://bundle/MyPart/EXIT_ID" />

That would cause the command's elementId to be looked up (and validated!) at runtime; mismatches could be reported.  (I guess either ApplicationElementImpl#[gs]etElementId() would need to hook in some resolver.)

But I see one possible problem: what should happen if the bundle is unloaded or replaced — and the identifier is now different?  I suppose since almost all objects now use references, it may only be an issue with fragment's imports.

[Incidentally, why is it that the e4xmi elements are plural? <commands/>, <handlers/>, <bindings/>, <addons/>…]

Brian.

On 31-Jan-2012, at 3:22 PM, Tom Schindl wrote:

> Hi Lars,
>
> I'm not 100% I really understand what you are suggesting here? Is that
> the tooling generates constants in an extra class?
>
> I'm also not sure what the URL modelid:// is good for? Did you e.g. know
> that you can simply use XPath on EMF-Models (we don't ship the bundle
> but it's part of the e4-git-repo).
>
> I think you need to elaborate a bit more, so that I can understand what
> you propose and how it could be implemented.
>
> Tom
>
> Am 30.01.12 23:12, schrieb Lars Vogel:
>> Hi,
>>
>> one thing I like about Android programming, is that you can refer to
>> static strings for ID's in a XML file (layout file) as well as in Java
>> code. In the layout file you use @id/button1to point to a ID defined in
>> a file.
>>
>> In your Android coding you could reference the ID via a static string.
>> This removes the issue that you may have typos either in your coding or
>> in your layout and allows consistent refactoring of ID's.
>>
>> One of the issues I believe still exists in todays Eclipse 4 plug-in
>> development, is that you have to define a ID twice, once in your
>> application model and at least once in your coding.
>>
>> I really liked the change to bundleclass:// in M5.
>>
>> Perhaps we could introduce another URI for ID which could be referred to
>> an ID defined in a file, e.g.
>>
>> modelid://Bundle-SymbolicName/path/filename.extension/id
>>
>> And add another annotation, like @ID, which allows to annotate static
>> strings and to mark them a ID's which could be used in the model as well
>> in the coding.
>>
>> @ID
>> public static final String part1 = "com.example.test.part1".
>>
>> Would that be helpful? Is it worth to open a enhancement request for this?
>>
>> Best regards, Lars
>> --
>> Lars
>> http://www.vogella.de - Eclipse, Android and Java Tutorials
>> http://www.twitter.com/vogella - Lars on Twitter
>>
>>
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