(Quick Reference)
addTo*
目的
Purpose
Adds a domain class relationship for one-to-many or many-to-many relationship, where the relationship is indicated by the property used as the suffix to the method.
使用例
Examples
def fictBook = new Book(title: "IT")
def nonFictBook = new Book(title: "On Writing: A Memoir of the Craft")
def a = new Author(name: "Stephen King")
.addToFiction(fictBook)
.addToNonFiction(nonFictBook)
.save()詳細
Description
The
addTo* method is a dynamic method that uses an association to automatically add instances to the association. It also automatically configures the bi-directional relationship so that both sides are set.
Consider these domain classes which are used in the example above:
class Author { String name static hasMany = [fiction: Book, nonFiction: Book]
}class Book { String title static belongsTo = [author: Author]
}The example creates a new fiction book and a new non-fiction book, and an author.
addToFiction is a dynamic method that works because the
Fiction part corresponds to the
fiction collection that results from the
hasMany declaration, and likewise for
NonFiction and
nonFiction. After calling
save() on the
Author, the associated
Book instances are transitively saved too, even though we didn't call
save() on either of them.
In addition, calling addTo* initializes the associated collections, and sets the back-reference of the
author property in each
Book.
There's also a more compact version of the method that accepts a
Map instead of a domain class instance:
def a = new Author(name: "Stephen King")
.addToFiction(title: "IT")
.addToNonFiction(title: "On Writing: A Memoir of the Craft")
.save()This works because GORM knows the type that is being added and can use the standard
Map constructor to create the instances for you.
