CODEWITHSUNDEEP
ruby-on-railsactiverecord
FeifanZ
FeifanZ

Reputation: 16316

Rails better way to get item by field from has_many association

Forgive me if this is a basic question; I'm learning Rails (using 3.2) as I go.

My Event model has_many images. Each image has an is_primary boolean field. Event should have a cover_image method, which returns the image with is_primary set to true, or the first image otherwise. This is my code:

def cover_image
    imgs = self.images
    imgs.each { |i| return i if i.is_primary }
    # If no primary
    return imgs.first
  end

I can't help feeling like there's a better way to do it, one that doesn't involve looping through all the elements just to find one.

Upvotes: 1

Views: 338

Answers (1)

Matt
Matt

Reputation: 14048

You could do this with a scope quite easily:

Image model

scope :primary, where(:is_primary => true)

Event model

def cover_image
  images.primary.first
end

This is a really basic example that should get you started at least, you'll want to build on it to handle a missing primary image gracefully, for example.

For completeness, you don't have to do this as a scope, if you'd prefer you can use where statements directly. Scopes are just really nice for staying DRY:

Event model

def cover_image
  images.where(:is_primary => true).first
end

Upvotes: 4

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