Question

in some video i saw next string:

User.select(:email).map(&:email)

tell me plz what does it means

i know that string

User.select(:email)

is selecting only the email column from the db, but i don’t understand what means

.map(&:email)

and can we change User.select(:email) to User.pluck(:email)

because from tutorial i understand thats the same methods. is this true?

Answer 1

The map(&:email) maps your array of Users to a map of string containing only the users’ emails.

The Array.map iterates over your current array, and creates a new one, by calling the parameter block, and storing the result in the new array. It is equivalent with this:

new_array = []
Users.select(:email).each do |user|
  new_array << user.email
end