ActiveRecord select except columns

问题

Is there a way I can specify to select ALL columns in ActiveRecord except just a few. For example, for a User, I don't want to select their password hash or their email. Is this possible or do I have to manually hardcode all columns?

Thanks

回答1:

write a scope like

def select_without columns
  select(column_names - columns.map(&:to_s))
end

回答2:

Something like this?

exclude_columns = ['password', 'email']
columns = User.attribute_names.delete_if(|x| exclude_columns.include?(x))

User.select(columns)

EDIT

I forgot that we can do Array1 - Array2

A best answer:

exclude_columns = ['password', 'email']
columns = User.attribute_names - exclude_columns

User.select(columns)

回答3:

Another really usefull way it's with a scope inside the model in case you need to avoid a column constantly.

In my case I save images into blob fields so I whant to avoid those to be loaded everytime and in a easy way:

scope :select_exclude_image, ->  { select( Movie.attribute_names - ['image'] ) }

Then to avoid the image in the selection you can do something like that:

Movie.select_exclude_image.first

or

Movie.select_exclude_image.all

I hope it will help!

来源：https://stackoverflow.com/questions/17431028/activerecord-select-except-columns