how to pass a map to function with keyword arguments

Question

I have a function like this:

pdfkit-clj.core/gen-pdf
 [html & {:keys [path tmp asset-path stylesheets margin orientation page-size], :or {path (:path defaults), tmp (:tmp defaults), asset-path (:asset-path defaults), margin {}, orientation (:orientation defaults), page-size (:page-size defaults)}}]

Now I'm trying to pass it a map with keyword arguments which doesn't work.

(let [gen_pdf_args {:tmp tmp_dir
                     :margin {:top 0 :right 0 :bottom 0 :left 0}}] 
        (gen-pdf html-black gen_pdf_args)
)

This issue is similar to turning a list into arguments.

The first linked question has three different approaches to solving the problem; I agree with the top answer that the best approach is to stay out of this situation by not writing functions to take unrolled keyword args, but if you can't change the function's interface then I think the second linked question has the best answer for how to work around the problem. — amalloy, May 16 '17 at 16:23

Alejandro C. · Accepted Answer · 2017-05-16T15:43:54.823

3

Using & {:keys [...]} actually doesn't expect you to call it with a map. Instead, you call it like (gen-pdf html :tmp tmp_dir :margin {:top 0}).

If you really want to use your map, you can use apply and flatten like (apply gen-pdf html-black (-> gen_pdf_args vec flatten)).

edited May 16 '17 at 15:43

answered May 16 '17 at 15:38

Alejandro C.

3,771
15
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I understand that. I'm building up the arguments programmatically or I want to set arguments in one go. – m33lky May 16 '17 at 15:43
See my edit. `apply` should solve your problem. – Alejandro C. May 16 '17 at 15:44
Yeah, I should use something light-weight for this instead of relying on external libs. – m33lky May 16 '17 at 16:53

score 1 · Answer 2 · answered May 16 '17 at 15:54

1

It sounds like you want something similar to the keyvals function:

(keyvals m)
 "For any map m, returns the keys & values of m as a vector,
  suitable for reconstructing via (apply hash-map (keyvals m))."

(keyvals {:a 1 :b 2})
;=> [:b 2 :a 1]
(apply hash-map (keyvals {:a 1 :b 2}))
;=> {:b 2, :a 1}

Notice that you still need to use apply like Alejandro said. You can find more information on keyvals here.

answered May 16 '17 at 15:54

Alan Thompson

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Yeah, this is good; just keep in mind that keyvals isn't part of core – Alejandro C. May 16 '17 at 16:03
3

Just use `(apply concat xs)` or `(mapcat seq xs)` instead of importing a whole big library to use `(keyvals xs)`. – amalloy May 16 '17 at 16:28

how to pass a map to function with keyword arguments

2 Answers2