Improve ObjectService with names for objects

[imagejan]

The ObjectService can be used quite flexibly to keep track of registered objects of any kind. To improve user experience, it would be useful to be able to specify names/identifiers for registered objects, though.

For example, the DefaultWidgetModel currently displays choice labels that are generated from each object's toString method:

scijava-common/src/main/java/org/scijava/widget/DefaultWidgetModel.java

Lines 225 to 233 in 06aa06d

	@Override
	public String[] getChoices() {
	final List<?> choicesList = item.getChoices();
	final String[] choices = new String[choicesList.size()];
	for (int i = 0; i < choices.length; i++) {
	choices[i] = choicesList.get(i).toString();
	}
	return choices;
	}

We could improve this by checking for the object's name via getName if the object implements org.scijava.Named. However, many objects we might want to register in practice don't implement this interface, e.g. RealTransform (from imglib2) or BdvHandle (from bigdataviewer) (@NicoKiaru, @tischi), Node (from sciview) (@kephale), or SpotCollection (from TrackMate).

To allow for more flexibility here, I'd like to suggest adding new API to ObjectService:

• void addObject(Object object, String name) allowing to add an object with a specified name, and
• Map<String, Object> getObjectMap() retrieving a map of names and objects.

In addition, we could change addObject(Object object) to automatically try getName and fall back to toString if no name is provided explicitly.

I vaguely remember that naming objects was mentioned in some discussion somewhere (maybe @ctrueden can recall better).

If that's a feasible change, we would most likely also need to change/improve the underlying ObjectIndex implementation.

[NicoKiaru]

Thanks for starting this discussion @imagejan !

I can recall a discussion on gitter here:
https://gitter.im/scijava/scijava-common?at=5d9c6278940b4c2fc096b63e

If you want to allow accessing Objects with a Map<String, Object>, you need to have unique names, right ? How would you do that ? Would you allow for non-unique names if the Objet class is different ?

[imagejan]

Thanks for linking to the discussion, @NicoKiaru!

Ah yes, Map<String,Object> probably wouldn't work without a lot of effort, and seeing how ObjectIndex is currently used (in PluginService, ModuleService etc.), I'd rather not mess with it ;-)

And I don't think we should disallow duplicate names, but rather leave it to the caller if they want to enforce uniqueness when adding objects.

We could maybe extend ObjectIndex by a new NamedObjectIndex (similar to SortedObjectIndex) and then just keep track of a Map<Object,String> for the names.

(The same object can be in the ObjectIndex multiple times, but that wouldn't matter for the map, as we'd have a single name per object.)

[ctrueden]

Thanks @imagejan for all your work on this.