How to set unique hasMany relations based class properties?

Question

I have two domain classes:

class Book {
  String name

  static hasMany = [articles: Article]
}   


class Article {
  String name

  static belongsTo = [book: Book]
}

I want to validate that a book does have only unique articals in terms of the article name property. In other words: there must be no article with the same name in the same book. How can I ensure that?

score 1 · Accepted Answer · answered May 04 '13 at 20:13

You can do this with a custom validator on your Book class (see documentation).

A possible implementation can look like this:

static constraints = {
    articles validator: { articles, obj -> 
        Set names = new HashSet()
        for (Article article in articles) {
            if (!names.add(article.name)) {
                return false
            }
        }
        return true
    }
}

In this example I am using a java.util.Set to check for duplicate names (Set.add() returns false if the same name is added twice).

You can trigger the validation of an object with myBookInstance.validate().

How to set unique hasMany relations based class properties?

1 Answers1