So I perform a query to the db and I have a complete array of objects:
@attachments = Job.find(1).attachments
Now that I have an array of objects I don't want to perform another db query, but I would like to filter the array based on the Attachment
object's file_type
so that I can have a list of attachments
where the file type is 'logo'
and then another list of attachments
where the file type is 'image'
Something like this:
@logos = @attachments.where("file_type = ?", 'logo')
@images = @attachments.where("file_type = ?", 'image')
But in memory instead of a db query.
This question is related to
ruby-on-rails
activerecord
Try :
This is fine :
@logos = @attachments.select { |attachment| attachment.file_type == 'logo' }
@images = @attachments.select { |attachment| attachment.file_type == 'image' }
but for performance wise you don't need to iterate @attachments twice :
@logos , @images = [], []
@attachments.each do |attachment|
@logos << attachment if attachment.file_type == 'logo'
@images << attachment if attachment.file_type == 'image'
end
have you tried eager loading?
@attachments = Job.includes(:attachments).find(1).attachments
If your attachments are
@attachments = Job.find(1).attachments
This will be array of attachment objects
Use select method to filter based on file_type.
@logos = @attachments.select { |attachment| attachment.file_type == 'logo' }
@images = @attachments.select { |attachment| attachment.file_type == 'image' }
This will not trigger any db query.
You can filter using where
Job.includes(:attachments).where(file_type: ["logo", "image"])
I'd go about this slightly differently. Structure your query to retrieve only what you need and split from there.
So make your query the following:
# vv or Job.find(1) vv
attachments = Attachment.where(job_id: @job.id, file_type: ["logo", "image"])
# or
Job.includes(:attachments).where(id: your_job_id, attachments: { file_type: ["logo", "image"] })
And then partition the data:
@logos, @images = attachments.partition { |attachment| attachment.file_type == "logo" }
That will get the data you're after in a neat and efficient manner.
Source: Stackoverflow.com