11: collection constraint (vector of foreign keys)
Let's say the forum you're building stores a user's favorite posts as a vector of foreign keys, like this:
{:username "birb"
:favorite-ids [1 2 3 4]}
Here's how you'd model this in Specmonstah:
(ns reifyhealth.specmonstah-tutorial.11
(:require [clojure.spec.alpha :as s]
[reifyhealth.specmonstah.core :as sm]
[reifyhealth.specmonstah.spec-gen :as sg]))
(s/def ::id (s/and pos-int? #(< % 100)))
(s/def ::post (s/keys :req-un [::id]))
(s/def ::favorite-ids (s/coll-of ::id))
(s/def ::user (s/keys :req-un [::id ::favorite-ids]))
(def schema
{:post {:prefix :p
:spec ::post}
:user {:prefix :u
:spec ::user
:relations {:favorite-ids [:post :id]}
:constraints {:favorite-ids #{:coll}}}})
There's our buddy :constraints again :) This time the constraint is :coll. This is used by the clojure.spec visitor to generate data correctly:
(defn ex-01
(sg/ent-db-spec-gen-attr {:schema schema} {:user [[1]]}))
(ex-01) ;; =>
{:p0 {:id 6}
:u0 {:id 9, :favorite-ids [6]}}
Specmonstah generated a post with :id 6, and sure enough you can see that the value of :favorite-ids is a vector containing the post's :id. But what if you want to generate multiple posts? Here's how you'd do that:
(defn ex-02
(sg/ent-db-spec-gen-attr {:schema schema}
{:user [[1 {:refs {:favorite-ids 3}}]]}))
;; =>
{:p0 {:id 6}
:p1 {:id 21}
:p2 {:id 8}
:u0 {:id 1
:favorite-ids [6 21 8]}}
And boom goes the dynamite. The key here is the map {:refs {:favorite-ids 3}} - this tells Specmonstah that this user will have 3 :favorite-ids.
You might be wondering, what happens if you generate 2 separate users, each with 3 :favorite-ids? Well my friend, wonder no more:
(defn ex-03
(sm/view (sm/add-ents {:schema schema}
{:user [[2 {:refs {:favorite-ids 3}}]]})))
Both users reference the same posts because Specmonstah generates the minimum data necessary to satisfy the query. You can also "manually" specify the ents you want to reference:
(defn ex-04
(sm/view (sm/add-ents {:schema schema}
{:user [[1 {:refs {:favorite-ids [:my-p0 :my-p1]}}]
[1 {:refs {:favorite-ids [:my-p2 :my-p3]}}]]})))
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