Question

I’ve got a class:

class Test {
    List<BigDecimal> values

    static constraints = {
    values(unique: true)
  }
}

However,

void testUniqueness() {
  List valList = [
   new BigDecimal(1),
   new BigDecimal(1)
  ]
  def testInstance = new Test(values: valList)
  mockForConstraintsTests(Test, [testInstance])
  assertFalse "Validation should fail for non-unique values", testInstance.validate()
}

This assert fails, because .validate() is true!

I want a list of BigDecimal’s which is unique to each instance of the Test object

Answer 1

This is not how it works. If you think about something simpler, e.g. “String username”, the uniqueness check creates a unique index in the database on that column. So two users cannot have the same username/login/etc.

But you’re asking for the contents of a List to be unique. The constraint (if it made sense) would compare two Lists and ensure that no two Test instances’ values lists are the same. For example [1, 3, 5] <-> [1, 3] would be ok, but [1, 3, 5] <-> [1, 3, 5] would fail. This would be impractical to implement and is not supported. It’s the equivalent of requiring that a username not repeat a letter – “burt” would be ok but “burtbeckwith” would fail.

If you want to have unique elements in a collection, just change it from a List to a Set. You don’t even need a constraint:

class Test {
   Set<BigDecimal> values
}