(newbie, but trying hard!)
I am designing a Woobly. A Woobly is non-trivial and has a number of
internal data structures (queues, worker threads etc.). You can 'add' and
'remove' jobs from a Woobly.
In OO land I might have a Woobly interface with the various methods which
provides a public API. I might also have a factory or more likely builder
somewhere which creates Wooblies.
The part I am struggling with is how to create a Woobly without exposing
its internals. Let's imagine that Woobly uses an internal
LinkedBlockingQueue of a certain size.
Option 1 - a big bag of data.
I could create a map of config/state/data that comprises the implementation
and have the creator function return that. Consumers can then call other
methods passing back that bag of config/state, but what stops them simply
diving into that bag themselves? For example:
[code]
(defn create-woobly
([] (create-woobly 100)
([queue-size] {:queue (java.util.concurrent.LinkedBlockingQueue
queue-size)}))
(defn add-job [woobly job] ....)
;; nothing stopping me diving into that state...
(.clear (:queue (create-wobbly)))
[/code]
Option 2 - protocol and deftype
Alternatively I could implement an IWoobly protocol and create a single
deftype which is instantiated and returned from the 'create-woobly'
function? I am not sure I like this as it is really back to OO isn't it?
I want to retain the notion of create returning a handle which is the first
argument in the other public functions, but the first way just feels far
too dangerous.
Am I overthinking this - what do you all do to address this?
Thanks a bunch.
Col
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