malli 2022-03-14 | Slack Archive

Martynas Maciulevičius13:03:04

Hey. What function should I use to parse a string into a number? Let's say I have this schema: (m/parse :int 15) My initial assumption was that the parse would do the string parsing. But it... doesn't work at all. How do I make this return 15 : (m/parse :int "15") Is this the right function to use?

ikitommi14:03:22

hi, it’s value transformation in malli, here are the docs: https://github.com/metosin/malli#value-transformation

Martynas Maciulevičius15:03:05

Thanks. That works.

Martynas Maciulevičius15:03:12

Why does parse exist then?

ikitommi16:03:29

it's structural parsing, please read the part from the README. Malli itself uses it for parsing Clojure destructuring syntax to infer schemas from source code.

✅ 1

Ryan Tate17:03:46

Is it possible to combine :and with :cat? In spec this would be "`&`" (ampersand). I need to check each key with :cat and then the two keys together via a special fn. This works without the :and but once I add the :and and the :fn it fails:

(m/validate [:* [:and [:cat :symbol :string] [:fn (fn [[key value]] true)]]]  '(regex "foo"))

Ultimate form is going to be like

'(regex "foo" xpath "bar" ...)

and I want :fn to check each pair. Thanks for any tips.

Ryan Tate17:03:52

Ack I don't think it will work anyway since the :cat does not produce the values for the next predicate as in spec. So even if I could make :and work it's not gonna give key/value to :fn. Hmm. Not sure how I can accomplish this. Maybe I can parse inside the validation

Ryan Tate17:03:01

OK I solved it like this, the special function is the inner one:

(m/validate [:fn (fn [seqn] (every? (fn [[key value]]  true) (m/parse [:* [:cat :symbol :string]] seqn)))] '(regex "foo" xpath "bar"))

👍 If anyone has a better idea just post here 🙃

Ryan Tate17:03:17

In order to make it work and composable with m/parse I think the schema will need to repeat the seqex. So parse will run 2x. Probably will still be faster than spec:

[:and [:fn (fn [seqn] (every? (fn [[key value]] true) (m/parse [:* [:cat :symbol :string]] seqn)))] [:* [:cat :symbol :string]]]

Ryan Tate17:03:46

Would still be nice if :and worked with cat though because then I could match multiple schemas across the same sequence. hmm

2022-03-14

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