(Quick Reference)
findOrCreateBy*
目的
Purpose
Dynamic method that uses the properties of the domain class to create query method expressions that return the first result of the query. This method behaves like
findBy except that it will never return
null. If a matching instance cannot be found then a new instance will be created and returned, populated with values represented in the query parameters. The difference between this method and
findOrSaveBy is that this method will not save a newly created instance where
findOrSaveBy does.
使用例
Examples
Given the domain class
Book:
class Book {
String title
String author
}The following are all possible:
def b = Book.findOrCreateByTitle("The Shining")
b = Book.findOrCreateByTitleAndAuthor("The Sum of All Fears", "Tom Clancy")
b = Book.findByAuthorInList(["Douglas Adams", "Hunter S. Thompson"])The following are roughly equivalent:
def b = Book.findOrCreateByTitle("The Shining")def b = Book.findByTitle("The Shining")
if (!b) {
b = new Book(title: "The Shining")
}詳細
Description
GORM supports the notion of
Dynamic Finders. The
findOrCreateBy* method finds the first result for the given method expression.
Because this method potentially creates a new instance and populates properties on that instance, only exact match criteria are allowed. For example, Book.findOrCreateByDate(dateValue) is valid but Book.findOrCreateByDateGreaterThan(dateValue) is not.
