rails way to join models

Question

Suppose I have a one-to-many association

in the Author class

has_many :books

in the School class

has_many :books

in the Book class

belongs_to :authors
belongs_to :schools

Now hitting the SchoolsController#some_method, with params[:id] as a get request parameter, I want to retrieve all the authors of books that are in some param[:id] school. So I wrote this that works

@shools = Books.where(school_id: params[:id])
@books ||= []
@books.each do |book|
   @books << book.user
end

but I don't think it is the correct rails way to do that. Could someone help ?

This question appears to be off-topic because it is about working code that needs refactoring. It should be on Code Review. — the Tin Man
– the Tin Man, Commented Mar 21, 2014 at 15:53

Marek Lipka · Accepted Answer · 2014-03-21 14:26:08Z

4

You should use joins method:

@authors = Author.joins(:books).where(books: {school_id: params[:id]})

answered Mar 21, 2014 at 14:26

Marek Lipka

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Comments

David Underwood · Accepted Answer · 2014-03-21 14:31:55Z

There area a few things wrong with your code.

First, the belongs_to params in your Book class should be singular. belongs_to :author and belongs_to :school

In your controller, you never use the @shools variable, I imagine it's supposed to read @books?

Appending to the @books array from within the each loop is a bad idea seeing as you're looping over @books in the first place.

Once you have all that fixed, you can get your authors back like this (as Marek mentioned in his answer):

@authors = Author.joins(:books).where(books: {school_id: params[:id]})

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