ActiveRecord find and only return selected columns

ruby-on-rails ruby-on-rails-3 rails-activerecord
timpone picture timpone · Oct 27, 2011 · Viewed 136.3k times · Source

edit 2

If you stumble across this, check both answers as I'd now use pluck for this

I have a fairly large custom dataset that I'd like to return to be echoe'd out as json. One part is:

l=Location.find(row.id)
tmp[row.id]=l

but I'd like to do something like:

l=Location.find(row.id).select("name, website, city")
tmp[row.id]=l

but this doesn't seem to be working. How would I get this to work?

thx

edit 1
alternatively, is there a way that I can pass an array of only the attributes I want included?

Answer

prasad.surase picture prasad.surase · Oct 11, 2012

pluck(column_name)

This method is designed to perform select by a single column as direct SQL query Returns Array with values of the specified column name The values has same data type as column.

Examples:

Person.pluck(:id) # SELECT people.id FROM people
Person.uniq.pluck(:role) # SELECT DISTINCT role FROM people
Person.where(:confirmed => true).limit(5).pluck(:id)

see http://api.rubyonrails.org/classes/ActiveRecord/Calculations.html#method-i-pluck

Its introduced rails 3.2 onwards and accepts only single column. In rails 4, it accepts multiple columns

Related questions

Rails update_attributes without save?

Is there an alternative to update_attributes that does not save the record? So I could do something like: @car = Car.new(:make => 'GMC') #other processing @car.update_attributes(:model => 'Sierra', :year => "2012", :looks => "Super Sexy, wanna …

Read More
ActiveRecord OR query

How do you do an OR query in Rails 3 ActiveRecord. All the examples I find just have AND queries. Edit: OR method is available since Rails 5. See ActiveRecord::QueryMethods

Read More
How to chain scope queries with OR instead of AND?

I'm using Rails3, ActiveRecord Just wondering how can I chain the scopes with OR statements rather than AND. e.g. Person.where(:name => "John").where(:lastname => "Smith") That normally returns: name = 'John' AND lastname = 'Smith' but I'd like: `…

Read More