What’s the normal way I should be handling speccing functions that have optional arguments?

generally you should use regex ops (like s/cat) to spec args and ops like s/? to handle optional arguments within that

Cool. Thanks 🙂

Is there a way to match an exact number of items in a collection or sequence? Let’s say I want to spec a seq or collection to have 3 and only 3 items in it?

I suppose I could always assert that in the spec for the fn that uses the collection.

As spec guide states 🙂 …

(s/def ::point (s/tuple double? double? double?))
(s/conform ::point [1.5 2.5 -0.5])
=> [1.5 2.5 -0.5]

tuple! Thank you.

s/tuple is good for heterogeneous fixed-size (“slotted”) vectors

s/coll-of with the :count option is good for homogenous (all items match the same pred) collections

like (s/coll-of double? :count 3)

That fits this use case better. Thanks, Alex.

either will work and they conform and gen pretty similarly but I think one or the other usually has a better match on intent

I’m attemping to make a spec for something that can either be any number of vectors, or 0 or 1 strings. currently I have (spc/or :vectortype (spc/* vector?) :stringtype (spc/? string?)) but that doesn’t really seem to be working. (I know this is whacky but, using it to learn the nuances of spec

Anyone see if I am doing something obviously wrong there?

Looks fair to me, what are you getting from that that makes you say it’s not working?

Getting a message in-console saying that the function call does not match the spec when the argument that that spec covers is just a string

Function arguments need to be inside (spc/cat ...) maybe you’re missing that?

I guess this would have been more useful- here is the whole spec for the function currently (spc/fdef typog :args (spc/cat :props map? :children (spc/or :vect (spc/* vector?) :stringt (spc/? string?))))

so I do have cat. but not sure if im using it right

Do you have the :ret key in your fdef too? I’ve seen odd results when that was missing.

Hmm I dont, ill try adding that

Everything else looks good to me, with the caveat that I’m still getting comfortable with spec myself, so I might be missing something.

I just threw a :ret any? in there, but same results sadly. Yeah. It seems to logically make sense to me, and to others I’ve showed it to. Something strange going on perhaps…

I appreciate your help 🙂

the s/or is not a regex op so inserts a new “level” of nesting

so that is always expecting 2 args with the first a map and the second either a collection of 0 or more vector or an empty collection or a collection containing one string

I don’t think that’s what you want

I suspect changing the or to alt is probably closer, would at least match the string case you want

but depends what you mean by “0 or 1 strings”

if you mean “no 2nd arg” for “0 strings”, then that case is already covered by (* vector?), which can be 0 vectors

Ahh it was alt! That is what I needed. I did gloss over that in the api but apparently that did not make enough sense for me. haha. Thank you alex.

Also good point about the case of the arg not being there handled by the *, that is definitely true.