[core] Added implementation of a ChannelGroupUID

[cweitkamp]

Initial idea and for discussion.

As preparation for a ChannelGroupBuilder which is accessible from the ThingHandlerCallback similar to the createChannelBuilder() or editChannel() methods I would like to introduce a ChannelGroupUID to identify the channel group to be created / edited.

• Added implementation and test of a ChannelGroupUID

Signed-off-by:Christoph Weitkamp github@christophweitkamp.de

[htreu]

Hi @cweitkamp can you please add some more context on what plans you have for a ChannelGroupBuilder? Right now there is now separate entity ChannelGroup.

[cweitkamp]

Yes, of course. Currently there is no easy way to create all channels for a specific ChannelGroupType. It has to be done manually by creating one channel after the other. I would like to introduce a new feature which can be used to create those channels all at once. An automatic approach needs access to the ChannelGroupTypeRegistry and/or the ChannelTypeRegistry which is not allowed for a binding.

I am not sure if we need a real builder for it or if we even need a ChannelGroup entity. We maybe can e.g. just return a list of ChannelBuilders.

public List<ChannelBuilder> createChannelGroupBuilder(ChannelGroupUID channelGroupUID, ChannelGroupTypeUID channelGroupTypeUID) {
    ChannelGroupType channelGroupType = channelGroupTypeRegistry.getChannelGroupType(channelGroupTypeUID);
    if (channelGroupType == null) {
        throw new IllegalArgumentException(String.format("Channel group type '%s' is not known", channelGroupTypeUID));
    }
    List<ChannelBuilder> channelBuilders = new ArrayList<>();
    for (ChannelDefinition channelDefinition : channelGroupType.getChannelDefinitions()) {
        ChannelType channelType = channelTypeRegistry.getChannelType(channelDefinition.getChannelTypeUID());
        if (channelType != null) {
            ChannelUID channelUID = new ChannelUID(channelGroupUID, channelDefinition.getId());
            channelBuilders.add(ThingFactoryHelper.createChannelBuilder(channelUID, channelType, configDescriptionRegistry));
        }
    }
    return channelBuilders;
}

[cweitkamp]

@htreu Since I already posted an initial code snippet I have created some working code too.

https://github.com/cweitkamp/smarthome/compare/feature-channelgroupuid...cweitkamp:feature-channelgroupbuilder

[htreu]

Thanks for the example. This looks pretty good and straight forward.
Is there a real need for the builder right now? Or do you want to provide this feature from the framework so that future binding developments can use it?
Why I ask: imho we should only have code which is actively used. Maintaining it should be justified by actual usage.

[cweitkamp]

I am with you. Unused code is just a millstone around the neck. But of course I have a use case for it.

The OWM binding (#5694) supports different forecast strategies (hourly / daily). Currently I decided to use a fixed number of hours (24) / days (5) to be requested whereas the OWM API is capable of delivering more data (max. 5 days / hour forecast and 16 days / daily forecast). Instead of defining fixed numbers I want to add configuration parameter for them. This should make it possible for everyone to adopt the number of forecasted hours / days for their own needs.

To archive my goal it would be nice to have an easy way to create a dynamical number of channel groups.

[htreu]

Yes, I just started to review the OWM binding and realised your needs in this. Thanks for the explanations.
I will merge here, so you can go on with the rest of the puzzle ;-)

[kaikreuzer]

Although this is already merged, please allow me two comments that I think should be addressed.

[kaikreuzer]

Typo: This should be SEPARATOR

[cweitkamp]

Hehe, that is a little copy&paste error from ChannelUID 😉. I will change it.

[kaikreuzer]

This is not in line with what the ChannelGroupTypeUID expects as a channelGroupUid (String) parameter - the separator should NOT be part of the UID (that anyhow looks a bit weird to me).

[cweitkamp]

Okay. I prepare a follow up to remove the # at the end.

[cweitkamp]

See #6157