Validation block

Regardless of the DSL expressivity, you may still have preprocessing logic that cannot be defined as a grules rule. Such logic can be always placed in a validate block which should return a map of clean values processed by this block or throw a ValidationException if any of the values fail validation. For example:

GET:
id toInt
...
name trim

validate {
  def sum = ($options.collect { // options is an HTTP array parameter
    it == ‘Yes’ ? 1 : 0
  }).sum()
  if (sum <= 1) {
    throw ValidationException(NOT_ENOUGH_OPTIONS, 
        ‘Please choose more options’, ‘options’)
  }
  // return two clean parameters
  [options: $options, chosenOptionsNum: sum]
}

POST:
...

validate { 
  ...
}
```