Question

Assuming i have the following grail domain entities:

class A { ... }

class B { ... }

In a third entity i have a one to many relationship as follows:

class C {
    static belongsTo = [a: A, b: B]

    static constraints {
        a unique: 'b'
    }
}

Is it possible in grails to define a unique relationship based on both properties (a and b) in class C, so no two C instances may be created having the same combination of a and b?

EDIT: My test case has as follows:

void testCompositeUniqueConstraint() {
    A a = // ...
    B b = // ...
    C existing = // ...
    existing.a = a
    existing.b = b
    mockForConstraintsTests(C, [existing])

    C c = // ...
    c.a = a
    c.b = b

    assertFalse c.validate()
}

On my test class i have included the @Mock([A, B]) annotation. I would expect this test to fail but it passes.

Answer 1

That’d be

static constraints = {
   a unique: 'b'
}

See http://grails.org/doc/latest/ref/Constraints/unique.html