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 <javascript:>> 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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