CODEWITHSUNDEEP
javagrailsgroovy
Bella
Bella

Reputation: 21

grails one-to-many relationship

I am new in grails and I need your help..

I have Author and Book domain classes:

class Author{

    static hasMany = [book:Book]

    String name
    //....
}

class Book{

    static belongsTo = [author:Author]

    String title
    //....
}

Domain classes have their controllers with "new" action, wich creates new object and save in db. In my browser when I enter .../myApp/author/new?name=myName&... , in my db creates author object, but when I enter .../myApp/book/new?name=title&.. it can not save book object,maybe because I have not got author object yet...

What can i do in this situation? If anyone know solution please help...

Upvotes: 1

Views: 3518

Answers (3)

BadSkillz
BadSkillz

Reputation: 2003

For testing purpose you can load some data into the bootstrap:

class BootStrap {
  def init = { servletContext ->
    def writer = new Author(name:"Jane")
    writer.save()
    if(writer.hasErrors()){
       println writer.errors
    }
    def comic = new Book(name: "superman", Author: writer)
    comic.save()
    if(comic.hasErrors()){
       println comic.errors
    }
  }
def destroy = {}
}

This way your app will have an Author and a Book in it.

Also this tutorial helped me very much.

Upvotes: 0

Hoàng Long
Hoàng Long

Reputation: 10848

When defining Book belongsTo Author, and the Author hasMany books, the Book can not be created without the author. Often you should do things like this:

  • Create Author
  • Create books
  • Add books to Author
  • Save author -> cascading books saved automatically.

As I see you describe your problem, I think you should go slower and take a look over the basics of Grails GORM (Groovy Object Relation mapping), you can start by examples with "Getting started with Grails", or read the 3 post about GORM Gotchas. They are very comprehensible.

Upvotes: 1

hvgotcodes
hvgotcodes

Reputation: 120198

You need to pass in the id of the Author to which you want to associate the Book instance. You need to then load the Author, and associate it with the Book you want to save.

im pretty sure you can't have a controller action named 'new'. 'new' is a reserved keyword in java/groovy.

def blah = new Blah()

Upvotes: 4

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