CODEWITHSUNDEEP
grailsgrails-orm
Sagarmichael
Sagarmichael

Reputation: 1624

Grails returning one element from each object

I am trying to just return a single string from each object.

Given the following:

 class Book {
String title
Date releaseDate
String author
Boolean paperback
}

for every instance of Book I want to get an array of authors then make them unique. I thought you could do something like:

def authors =  Book.findAllByAuthor()

This just gives me an array off book objects. I know i can do a 

a =[]
authors.each{a.add(it.author)}
a.unique()

I am almost certain there is a way just to grab all authors in one line.

any ideas?

Upvotes: 0

Views: 104

Answers (2)

lukelazarovic
lukelazarovic

Reputation: 1502

This gives you distinct authors of any book:

  Book.executeQuery("select distinct author from Book")

Upvotes: 1

Joshua Moore
Joshua Moore

Reputation: 24776

You can use projections to get a distinct list of authors across all books. Take a look at the createCriteria documentation for more examples.

def c = Book.createCriteria()
def authors = c.list() {
  projections {
    distinct('author')
  }
}

Upvotes: 1

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