merge won't help as there will be name space clashes.
I wonder if a more elegant approach would be to construct the 'inner'
system and then assoc onto it the external dependencies it needs
before calling start.
On 11 March 2015 at 18:49, <adrian.med...@mail.yu.edu> wrote:
> I believe I misunderstood your question; I didn't realize it was system (as
> opposed to any general component) specific. I think systems can be merged
> together (via 'merge'). Would that help?
>
> On Wednesday, March 11, 2015 at 2:40:14 PM UTC-4, Colin Yates wrote:
>>
>> Hi Adrian - I don't follow how that helps integrate two different
>> systems - I wonder if my question was unclear or I am missing
>> something in your answer. Would you mind posting some pseudo code to
>> clarify please?
>>
>> On 11 March 2015 at 18:32, <adrian...@mail.yu.edu> wrote:
>> > You can specify component dependencies using the 'using' function as you
>> > know. As long as you know the key of the component in the system you can
>> > specify this dependency wherever you construct the component. If you
>> > want to
>> > parameterize dependencies, write a constructor function which takes the
>> > external dependency as a value.
>> >
>> > On Wednesday, March 11, 2015 at 2:17:12 PM UTC-4, Colin Yates wrote:
>> >>
>> >> I have a non-trivial component which requires a bunch of internal and
>> >> external collaborators to work. This component is itself re-usable.
>> >>
>> >> What I really want to do is have ReusableComponent be a component in a
>> >> system so it can pull its external collaborators. However,
>> >> ReusableComponent
>> >> constructs its own services etc. so it really want to be (or at least
>> >> have
>> >> access to) a system.
>> >>
>> >> For example, let's say I have the following:
>> >>
>> >> (defrecord InternalToReusableComponent [bus]
>> >> (component/Lifecycle
>> >> (start [this]...))
>> >>
>> >> (defrecord ReusableComponent [bus logger]
>> >> (component/Lifecycle
>> >> (start [this]
>> >>
>> >> this)
>> >> ....))
>> >>
>> >> (defn reusable-component-system [external-collaborator]
>> >> (component/system-map
>> >> :bus (....)
>> >> :logger (....)
>> >> :reusable-component (component/using (map->ReusableComponent {})
>> >> [:bus
>> >> :logger external-collaborator]))
>> >>
>> >> Fine - I now have a system from which I can pull the reusable
>> >> component.
>> >> However, where does 'external-collaborator' come from? Obviously there
>> >> is a
>> >> larger system which I want this component to be part of so I can do:
>> >>
>> >> (defn larger-system []
>> >> (component/system-map
>> >> :external-collaborator (...)
>> >> :reusable-component (component/using (some-magic-glue)
>> >> [:external-collaborator])))
>> >>
>> >> I am struggling to see what (some-magic-glue) should be. I imagine it
>> >> needs to be something like:
>> >>
>> >> (defrecord SystemAdaptor [external-collaborator internal-system]
>> >> component/Lifecycle
>> >> (start [this]
>> >> (let [internal-system (or internal-system
>> >> (reusable-component-system
>> >> external-collaborator))
>> >> internal-system (component/start internal-system)]
>> >> (assoc this :internal-system internal-system)))
>> >> (stop [this]
>> >> (let [internal-system (:internal-system this)
>> >> internal-system (component/stop internal-system]
>> >> (assoc this :internal-system internal-system)))
>> >>
>> >> but it all feels a bit yuck.
>> >>
>> >> I can't merge the two systems because the reusable component is chocka
>> >> full of very fine grained command handlers and both the internal and
>> >> external systems will have their own 'bus' for example. I could
>> >> namespace
>> >> the keys but that again feels painful...
>> >>
>> >> Hope that is clear - and I look forward to your thoughts :).
>> >
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