I have a protocol that a generic rendering method uses:
```
(defprotocol Styled
(css-class [this])
(contents [this]))
```
and I want plain cljs maps to implement it. As I have constantly
re-learned, there are two map types, so I currently have two `extend-type`
clauses:
```
(extend-type PersistentArrayMap
Styled
(css-class [_]
"fig-map")
(contents [value]
(map (fn [[key value]]
(MyMapEntry. key value))
value)))
(extend-type PersistentHashMap
Styled
(css-class [_]
"fig-map")
(contents [value]
(map (fn [[key value]]
(MyMapEntry. key value))
value)))
```
but this makes changes to how maps implement `Styled` a bit perilous and
tedious. In Java-land, I could lean on `clojure.core/extend`:
```
(let [map-styled
{:css-class (constantly "fig-map")
:contents (fn [value]
(map (fn [[key value]]
(MapEntry. key value))
value))}]
(extend PersistentArrayMap
Styled
map-styled)
(extend PersistentHashMap
Styled
map-styled))
```
but this doesn't appear to be a thing in ClojureScript.
Is there a language feature that allows for concise reuse of protocol
implementations across types? Or am I abusing protocols/creating my own
problems by attempting to extend the myriad built-in Clojure types to a
protocol? (and how should I be framing a solution)?
I did find this mailing list topic from a few years back:
https://groups.google.com/forum/#!topic/clojurescript/GZypP_YV4l0
which I read as saying that `extend` is tricky to implement (and I think
`specify` might be missing the mark for my use case).
Thanks!
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