Custom Validator Function for AJV

A running example

Zendro generates a validations/<model>.js file for every model, using AJV to check each attribute’s basic type (e.g. "river_id": { "type": ["string"] }). Beyond that, you can add custom asynchronous validation logic for any attribute using the asyncValidatorFunction keyword — a Zendro-registered AJV keyword whose value is your own async function.

A running example

Say we have a model called example with an id attribute, and we only want to accept the literal value "1".

In validations/example.js, generated code already looks like this (the exact attributes will differ per model):

module.exports.validator_patch = function(example) {
  example.prototype.validationControl = {
    validateForCreate: true,
    validateForUpdate: true,
    validateForDelete: false,
    validateAfterRead: false
  }

  example.prototype.validatorSchema = {
    "$async": true,
    "type": "object",
    "properties": {
      "id": {
        "type": ["string"]
      }
      // ...other attributes
    }
  }

  example.prototype.asyncValidate = ajv.compile(
    example.prototype.validatorSchema
  )

  // validateForCreate/validateForUpdate/validateAfterRead all call
  // asyncValidate(record) - see the generated file for the full contents.

  return example
}

Add asyncValidatorFunction to the id property inside the existing validatorSchema.properties object — don’t replace the whole file, just extend what’s already there:

"id": {
  "type": ["string"],
  "asyncValidatorFunction": async function(data) {
    if (data === "1") {
      return true
    } else {
      return new Promise(function(resolve, reject) {
        return reject(new Ajv.ValidationError([{
          keyword: 'asyncValidatorFunction',
          message: `${data} is not 1`
        }]))
      })
    }
  }
}

See also Customize Zendro for how this fits into the broader customization workflow.

Custom Validator Function for AJV

Table of contents

A running example