I have similar case with CANopen and I did register different instances of callback for each subscription: https://github.com/splatch/canopen-cmi-uvr-playground/blob/master/reader/src/main/java/brute/force/scanner/UVR16Printer.java#L125L136
I believe the ultimate solution would be access to actual field instance through subscription event. Currently it is (in theory) doable through: String name = event.getFieldNames().iterator().next(); // in case of wildcard subscription name doesn't matter much PlcField field = event.getFiled(name); I know it is a bit awkward - but it does work with current API. Even if an subscription might bring 1..N updates for bus systems it is usually 1..1. Exceptionally, even with group addresses supported by KNX you'll probably have 1..1 event as whole invention is to reduce bus load. Maybe it is good idea to have different field type for groups? I was also thinking of how to handle "patterns" for CANopen. there are heartbeat events sent by nodes. I assumed that nodeId==0 means all nodes and nodeId > 0 means specific node. There is just one case when field becomes a wildcard and it does not require extra regexp. My point in all above is to balance amount of regexps, cause they might differ between languages and become a trouble above certain complexity threshold. Best, Łukasz On 13.11.2020 13:55, Christofer Dutz wrote: > Another thing a came across, was that with subscriptions (at least for KNX) > it makes sense to have field addresses that allow matching multiple values. > > For example if I have an address */*/12, I get all the actual temperature > values for all rooms in my house. > > The problem now is, that if I simply return a PlcValue (or multiple) ... we > no longer know which address a value belongs to. > > So I was thinking: > - We distinguish between pattern-fields and normal fields. Normal fields > identify only one element, Pattern Fields can identify multiple values. > - If a normal field is used, a normal PlcValue is returned > - If a pattern field is used, a PlcStruct is returned (even if it's only one > element) where the name of the property name is a stringified representation > of the address and the value is the PlcValue > > Does this make sense? > > > Chris > > > Am 12.11.20, 23:15 schrieb "Łukasz Dywicki" <[email protected]>: > > Looking at subscription methods - I am not sure if there is one standard > which can support all three kinds at the same time. > Some kind of distinguish is necessary, but for an end user (counting > myself) - multiple types of subscription happening at the same time are > rather unlikely to happen. > > Looking from canopen perspective - there is possibility to subscribe to > some messages happening directly on the bus if plc4x becomes a so-called > master node (that's the way its implemented currently using EVENT > subscription kind). > There is also possibility to subscribe over coordinator node which is > specified by yet another specification which number I don't remember > right now. In theory - we could also subscribe to other node messages > since canbus is still a bus system so everyone sees everything. > Later two cases are currently left unimplemented. > > Best, > Łukasz > > > On 12.11.2020 18:33, Christofer Dutz wrote: > > Hi all, > > > > I’m currently implementing the different subscription types in KNX4Go … > and here I noticed something. > > We create a SubscriptionRequestBuilder and here can add different types > of fields and even combinations. > > So we could create a subscription request with some on-value-change > fields, some periodically pulled fields and some events/alarms. > > > > Now does it actually make sense to have this sort of combinations? I > mean the program processing the results has to be very flexible in this case. > > > > Wouldn’t it make sense to have 3 different types of subscription > requests? > > > > Chris > > >
