How to compose different json jbuilder views?

Question

Say I have Library and Book models in Rails 4.

I also have a book.json.jbuilder file that defines how Book should be rendered in json.

How can I tell library.json.jbuilder to reuse book.json.jbuilder for rendering book json instead of duplicating the code?

#library.json.jbuilder example
json.(@libraries) do |library|
    json.id library.id
    json.name library.name
    # instead of the line below, is it possible to tell jbuilder 
    # to render books using book.json.jbuilder?
    json.books library.books, :title, :author 
end

Answer 1

This can be achieved using partials.

See the example below with _book.json.jbuilder and a _library.json.jbuilder partials.

More documentation here: https://github.com/rails/jbuilder

# books/_book.json.jbuilder
json.id book.id
json.title book.title
json.author book.author

# books/index.json.jbuilder
json.array! @books, partial: 'books/book', as: :book

# libraries/_library.json.jbuilder
json.id library.id
json.title library.name
json.books library.books, partial: 'books/book', as: :book

# libraries/index.json.jbuilder
json.array! @libraries, partial: 'libraries/library', as: :library