Custom validation

You can add custom validation with evalValidators instruction.

evalValidators?: {
    errorCodes: {
      code: string;
      message: string;
    }[];

    /**
     * Special props:
     * - $val
     * - $error
     * - $form
     *
     * Example:
     *  if (!$val.firstName || $val.firstName.length !== 6) throw [new $error('prop/is-exact-length', { length: 6 })]
     */

    $evals: string[];


    /**
     * Form value dependencies. You can put asterisk at the end.
     * Example:
     *  - a.b.c
     *  - a.b.c.d.f.g.h
     *  - a.d[]
     *  - a.d[].r.t[].d
     *
     *  If you need * support ask for it.
     */
    dependencies?: string[];
  };

A + B = C example

{
  "$theme": "rounded/blue",
  "schema": {
    "type": "object",
    "properties": {
      "a": {  "type": "number" },
      "b": {  "type": "number" },
      "ab": { "type": "number",  "evalValidators": {
          "errorCodes"  : [
            {
              "code"   : "custom",
              "message": "NOPE"
            }
          ],
          "$evals"      : [
            "if (($val.a + $val.b) !== $val.ab) { throw new $error('custom') }"
          ],
          "dependencies": [ "a", "b" ]
        }}
    }
  },
  "layout": {
    "type": "div",
    "items": [  {  "key": "a" }, { "type": "span", "title": "+" }, {  "key": "b" }, 
    { "type": "span", "title": "=" }, {  "key": "ab" }  ]
  }
}