I would generally handle this sort of encapsulation at the namespace level.
Put (create-woobly) and (add-job) and all the other woobly-related
functions into a woobly namespace. Also add any functions that access info
from a woobly bag-o-state, or mutate a woobly to make a woobly-with-extras.
Functions that might dangerously expose internals of a woobly can be made
private, or possibly you can just document them in a way to warn folks away
from "bad" behaviour.
While external users of (woobly/create-woobly) can in theory dig into the
internals of the woobly "object", but it should be relatively obvious that
this isn't a good idea.
I'd defer making protocols until you actually need polymorphism.
- Korny
On 10 May 2013 03:03, Colin Yates <colin.ya...@gmail.com> wrote:
> Thanks for all the helpful responses.
>
> One reason I want to hide the internals is that I don't want people to add
> jobs directly to the queue. (add-job) will put a map containing the
> provided function onto the queue. Not really relevant, but this is so that
> I can track queue timings that I can later on use to determine how much
> capacity the system can handle.
>
> I am nervous as well about "expose internals but trust people to do the
> right thing" because in this case, if I was a consumer and saw that queue,
> particularly given the emphasis about data being the contract etc. then why
> would I think *not* to use it.
>
> I do appreciate the point about not needlessly obfuscating information -
> this is a slightly different case.
>
> Sounds like in this case, either reify is the way to go or maybe return a
> bad of data but have this stuff in an 'internal' map (i.e. {:internal
> {:queue...}})
>
> Thanks a bunch - really helpful.
>
>
> On 9 May 2013 17:30, James Reeves <ja...@booleanknot.com> wrote:
>
>> On 9 May 2013 17:07, Colin Yates <colin.ya...@gmail.com> wrote:
>>
>>> The part I am struggling with is how to create a Woobly without exposing
>>> its internals.
>>>
>>
>> To what end? What's the benefit?
>>
>> If you take a look at some internal data structures Clojure uses, like
>> zippers or protocols, you'll notice that they're just maps. In general
>> there's no need to try and obfuscate data to stop people from diving into
>> the internals; just don't provide a public API for the internal parts and
>> people will get the hint.
>>
>> - James
>>
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