Grailsが属する使用する

Grails Belongsto Use

Grails3はTo、多対1の関係に属します

参照：http：//docs.grails.org/latest/ref/Domain%20Classes/belongsTo.html

オブジェクトの説明：

著者：著者

本：本

本は著者のものです

static belongsTo There are two ways to use it:

method one: static belongsTo = Author //[Domain1,Domain2] There is no reference in this way, the database does not build indexes and foreign keys. Feeling is useless, but it must be specified in many-to-many, otherwise it is abnormal. domain: 

class Author { String name  static constraints = { } }

class Book { static belongsTo = Author String title  static constraints = { } }

 Database: Page: ========================================================================================

Method 2:  static belongsTo = [author:Author]//[doamin:Domain1,domain2:Domain2]  Or: Author author static belongsTo = Author This way the database Book table will establish the Author's index and foreign key (author_id) 

doamin: 

class Author { String name  static constraints = { } }

class Book { static belongsTo = [author: Author] String title  static constraints = { } }

database:

page:

The author field is added to the page and can be used for relationship maintenance between book and author.