Grails -> GORM -> forcing only one

Question

I'm trying to ensure there is only one row record for the following entity:

class CreditType {

String name

String external_id

Boolean usedForWaivedFee = Boolean.FALSE // default to false

static hasMany = [credits: Credit]

  static constraints = {
   external_id unique: true
   name unique: true
  }
}

Or, put another way, I'm trying to ensure there is only one row with "usedForWaivedFee" is true.

The best idea I have is: custom validator in contrainsts which loops through all current CreditType and ensures there isn't any existing.

Thoughts?

Any suggestions?

Answer 1

Instead of looping through all the instances, you can use countBy method in custom validator. For example, you can use following custom validator

static constraints = {

        usedForWaivedFee validator: { val, obj ->
            if (val) {
                if (CreditType.countByUsedForWaivedFee(Boolean.TRUE)) {
                    return false
                }
            }
            return true
        }
}