While reading the clojure.java.jdbc code yesterday, I discovered to my
surprise that map destructuring can be used after an & in an arglist.
This should give you all the described benefits of the two approaches you
mention
((fn [a & {:as d}] d) 1 :opt1 'blah :opt2 false)
You can also do defaults using :or - although these defaults don't get
merged into the value of :as - so an explicit (merge) might be better.
((fn [a & {:keys [misc] :or {misc :misc-default} :as d}] [d misc]) 1 :opt1
'blah :opt2 false)
Hope that makes sense!
Glen
On Friday, 25 April 2014 23:41:22 UTC+1, Colin Fleming wrote:
>
> Hi all,
>
> I'm working on an API at the moment, and I'm balancing whether to use
> inline keyword args which I would destructure in the functions, or whether
> to just pass an explicit params map as the last parameter. Comparison of
> the two options in case I'm not explaining myself well:
>
> Kwargs:
> (class/create-class :instance list
> :description "My description"
> :implements (keys class-methods)
> :methods (calculate-my-methods))
>
> Map:
> (class/create-class {:instance list
> :description "My description"
> :implements (keys class-methods)
> :methods (calculate-my-methods)})
>
> A lot of APIs I've seen have favoured kwargs, and it undeniably makes for
> some pretty code - Seesaw is the best example I've seen here, the API is a
> thing of beauty. However it seems to me to have some issues:
>
> 1. If I want to delegate to another call from within an API function
> and use the same arguments, it's really awkward: (apply delegate
> (mapcat identity args)) or some similarly awful black juxt magic. Or
> of course writing out all the parameters again, but that's even worse.
> 2. It's more difficult to make parameters optional based on some
> runtime criteria since the params are baked into the function call. I
> guess
> this is usually dealt with by making the calls handle nil for a particular
> parameter.
>
> Both of these are much easier when passing an explicit map. Any
> preferences here, from either writing or using APIs like this?
>
> Cheers,
>
> Colin
>
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