validation of clojure schema

Question

i have a problem in validation of clojure prismatic schema. Here is the code.

:Some_Var1 {:Some_Var2  s/Str
                  :Some_Var3 ( s/conditional
                        #(= "mytype1" (:type %)) s/Str
                        #(= "mytype2" (:type %)) s/Str
                  )}

I am trying to validate it using the code:

"Some_Var1": {
    "Some_Var2": "string",
"Some_Var3": {"mytype1":{"type":"string"}}
  }

but it is throwing me an error:

{
  "errors": {
    "Some_Var1": {
      "Some_Var3": "(not (some-matching-condition? a-clojure.lang.PersistentArrayMap))"
    }
  }
}

It is a very basic code i am trying to validate. I am very new to clojure and still trying to learn basics of it.

Thanks,

Answer 1

Welcome to Clojure! It's a great language.

In Clojure, a keyword and a string are distinct types i.e. :type is not the same "type". For example:

user=> (:type  {"type" "string"})
nil
(:type  {:type "string"})
"string"

However, I think there is a deeper issue here: from looking at your data, it appears you want to encode the type information in the data itself and then check it based on that information. It might be possible, but it would be a pretty advanced usage of schema. Schema is typically used when the types are known ahead of type e.g. data like:

(require '[schema.core :as s])
(def data
  {:first-name "Bob"
   :address {:state "WA"
             :city "Seattle"}})

(def my-schema
  {:first-name s/Str
   :address {:state s/Str
             :city s/Str}})

(s/validate my-schema data)

I'd suggest that if you need validate based on encoded type information, it'd probably be easier to write a custom function for that.

Hope that helps!

Update:

An an example of how conditional works, here's a schema that will validate, but again, this is a non-idiomatic use of Schema:

(s/validate
{:some-var3
(s/conditional
 ;; % is the value: {"mytype1" {"type" "string"}}
 ;; so if we want to check the "type", we need to first
 ;; access the "mytype1" key, then the "type" key
 #(= "string" (get-in % ["mytype1" "type"]))
 ;; if the above returns true, then the following schema will be used.
 ;; Here, I've just verified that
 ;; {"mytype1" {"type" "string"}}
 ;; is a map with key strings to any value, which isn't super useful
 {s/Str s/Any}
)}
{:some-var3 {"mytype1" {"type" "string"}}})

I hope that helps.