CODEWITHSUNDEEP
grailsgroovygrails-orm
ses
ses

Reputation: 13372

how to made one-to-one bidirectional relationships in grails?

I have two domain classes and want to have one-to-one BIDIRECTIONAL relation between them. I write:


class Person {

  Book book;

  String name
  Integer age
  Date lastVisit

  static constraints = {
    book unique: true  // "one-to-one". Without that = "Many-to-one".
  }

}
 


class Book {

  String title
  Date releaseDate
  String ISBN

  static belongsTo = [person:Person] // it makes relationship bi-directional regarding the grails-docs 
}

So, i want to have bi-directional, i could NOT find link from Book to Person in generated SQL:


CREATE TABLE `book` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `version` bigint(20) NOT NULL,
  `isbn` varchar(255) NOT NULL,
  `release_date` datetime NOT NULL,
  `title` varchar(255) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM AUTO_INCREMENT=2 DEFAULT CHARSET=latin1

So then it means it is not bidirectional then? How to make bidirectional?

Upvotes: 1

Views: 5685

Answers (2)

Greedydp
Greedydp

Reputation: 205

To make this relationship one to one bidirectional,you should define them as fallows

     //Person is the owning side of relationship
     class Person {

      //a foreign key will be stored in Book table called person_id
      static hasOne = [book:Book]

      static constraints = {
        book unique: true
      }  
    }

    Class Book{
     Person person
    }

belongsTo is used for specifying the owner side(which manages relationship) of a one-to-many, many-to-one, or many-to-many relationship and for making relationship bidirectional

belongsTo should be used always in owned side

Upvotes: 1

z.eljayyo
z.eljayyo

Reputation: 1289

check out the hasOne property, in which class you define hasOne and belongsTo depends on where you want the FK to be stored, check this grails doc regarding hasOne: http://www.grails.org/doc/latest/ref/Domain%20Classes/hasOne.html

Upvotes: 3

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