Rails includes with scope

问题:

I have a model called Author. An author has many Articles. Articles have a scope called .published that does: where(published: true).

I want to load the author, with the published articles. I tried:

Author.includes(:articles.published).find(params[:author_id])

But that throws an error: undefined method 'published'. Any idea?

回答1:

I think the best solution would be:

Author.includes(:articles).where(:articles=>{published: true}).find(params[:author_id])

Or you can create scope:

class Author < ActiveRecord::Base 
    scope :with_published_articles, -> { includes(:articles).where(articles: { published: true}) }
end

and then:

Author.with_published_articles.find(params[:author_id].to_s)

回答2:

I would specify a scope on the Author called with_published_articles like this:

scope :with_published_articles, -> { joins(:articles).merge(Article.published) }

This will resolve your problem to also specify the where(active: true) on your Author model in case the published behaviour of and Article will change in the future.

So now you can call:

Author.with_published_articles.find(params[:author_id])

回答3:

Try this code:

Author
  .includes(:articles).where(published: true).references(:articles)
  .find(params[:author_id])

Here you can find more information about the example above: includes api doc

回答4:

Using:

class Articles < ActiveRecord::Base 
    scope :published, -> { where(articles: {published: true}) }
end

Define a scope on Autor

class Author < ActiveRecord::Base 
    scope :with_published_articles, -> { joins(:articles).merge(Articles.published) }
end

Or

Author.joins(:articles).merge(Articles.published).find(params[:author_id])