How to filter a models field by multiple values (OR'd)

Question

I have a model say Book which has the following scope function:

scope :author, lambda { |author|
    return where(nil) unless author.present?
    joins(:author).where('author.id' => author)
  }

This can filter the Books with only ONE author value. What I want to do is that I am passed a array from a JavaScript file which is a list of authors for example: ["harry", "doyle", "alex", "parrish"] and I want to be able to find all the books who has ANY of these authors (so an OR query here). Note each book can have multiple authors.

I have tried the following function but it simply gives me all the books rather than filtering correctly as I stated above.

scope :authors_multiple, lambda { |authors|
  @results = Book
  authors.each do |auth|
    @results = @results.author(auth)
  end
  return @results
}

model Author (extract):

class Author < ApplicationRecord
  has_and_belongs_to_many :books, uniq: true
  ....

model Book (extract):

class Book < ApplicationRecord
  has_and_belongs_to_many :authors, uniq: true
  ....

Can you please help me understand what I am doing wrong or what may be the right way to do it. Thanks in advance.

Answer 1

authors = ["harry", "doyle", "alex", "parrish"]  
Book.where(author: authors)

or

authors = ["harry", "doyle", "alex", "parrish"]  
auths = Author.where(name: authors)
Book.where(author: auths)

This assumes that an Author has many Books. You can learn more about model associations here: https://guides.rubyonrails.org/association_basics.html

Answer 2

First you need to get your Author records. How this is done depends on your schema and data, but it will be something akin to:

author_names = ["harry", "doyle", "alex", "parrish"]

Then one of the following:

authors = Author.where(name: author_names)
authors = Author.where("name ILIKE ANY ( array[?] )", author_names.map { |name| "%#{name}%" })

Something that gets us an ActiveRecord::Relation of the authors we need. Once we have the authors we can merge that with our books to get all the books we want:

books = Book.joins(:authors).merge(authors)

Note that the join is on the plural authors. Rails will know to join through the join table (should be authors_books by default) to the authors table.

Answer 3

You get an array of author names, right?

scope :by_author, lambda { |names|
  # if you have a chance to get blank values you need to reject them
  names.reject!(&:blank?) if names.is_a? Array

  joins(:authors).where(authors: { name: names }).distinct if names.present?
}

It should work properly with array or string argument

Book.by_author(["harry", "doyle"])
Book.by_author("harry")

Answer 4

Try Below code:

authors = ["harry", "doyle", "alex", "parrish"]    
Book.joins(:authors).where(:authors => {:name => authors})