Grails，gorm。通过 parent 查找 child，通过 child 查找 parent

Question

例如，我parentclass作者：

class Author {    
    String name
    static hasMany = [
         fiction: Book, 
         nonFiction: Book
    ]
}

和一本childclass书：

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

我已经为作者做了一些记录：

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()

如何找到 parent 的 child-class 记录和 child 的 parent-class 记录？

Answer 1

在我看来，这不是对数据建模的最佳方式。我会这样做。

class Author {    
  String name
  static hasMany = [books: Book]
}

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

enum BookTypes {
  FICTION,
  NON_FICTION
}

然后，您可以像

这样进行查找

def author = Author.get(1)
def nonFictionByAuthor = Book.findAllByAuthorAndBookType(author, BookTypes.NON_FICTION)

你也可以这样做...

def author = Author.get(1)
def fictionBooks = author.books.findAll { it.bookType == BookTypes.FICTION }

然后反过来：

def fictionBook = Book.findByTitleAndBookType('Title001', BookTypes.FICTION)

Grails，gorm。通过 parent 查找 child，通过 child 查找 parent

Grails, gorm. Find child by parent and parent by child

grails

grails-orm