Conditional validation (if transformer)

Before we get into composition, let’s have a look of conditional validation.

validation.validate('NA', {if: "$value != 'NA'", validate: /id\d+/, message: 'invalid id format'});
// => undefined
validation.validate('xx', {if: "$value != 'NA'", validate: /id\d+/, message: 'invalid id format'});
// => [ 'invalid id format' ]
validation.validate('id23', {if: "$value != 'NA'", validate: /id\d+/, message: 'invalid id format'});
// => undefined

We only support expression in if condition check, not function. This is to support an edge case that user really want to validate a property named “if” in the model. We will show example of this edge case in summary.

Conditional validation was implemented as if transformer. We will explain more in transformer rule.

When bcx-validation sees that conditional rule above, it transforms it into:

validation.validate('NA', [
  {validate: 'skipImmediatelyIf', value: "!($value != 'NA')"},
  {validate: /id\d+/, message: 'invalid id format'}
]);

You can see we will rarely use skipImmediatelyIf directly, if transformer does the job, and makes the whole rule short and neat.

if transformer can wrap chain of rules too. Here is a rewrite of the previous chain rule.

var rule = {
  if: "$value != 'NA'",
  group: [
    // 'mandatory' validator is almost same as {validate: 'failImmediatelyIf', value: '_.isEmpty($value)', message: 'must not be empty'},
    'mandatory',
    [
      {validate: /[a-z]/, message: 'must contain lower case letter', stopValidationChainIfFail: true},
      {validate: /[A-Z]/, message: 'must contain upper case letter', stopValidationChainIfFail: true},
      {validate: /\d/, message: 'must contain digit'}
    ],
    {validate: /_/, message: 'must contain underscore'}
  ]
};

Let’s move on to validator composition.