Best practice to create a new array from another array in Ruby

Question

Here is my code that works but I'm looking for a solution thats even cleaner. Im trying to avoid having to initalize my array first.

users = []
employees_to_import.each do |employee|
  users << User.new(employee.slice(:first_name, :last_name, :email))
end

Is there a method in ruby that I can call to do something like this?

users = employees_to_import.push_each do |employee|
  User.new(employee.slice(:first_name, :last_name, :email))
end

Not sure if a method like this exists, I didn't see anything in the docs but I figured I would ask.

You could use Enumerable#each_with_object: employees_to_import.each_with_object([]) { |employee, users| users << User.new(employee.slice(:first_name, :last_name, :email)) }. Here map (as @AmitA has used) is preferable, but each_with_object is the method of choice in many other situations. Among other things (pertaining to scope), each_with_object avoids the need to first define the object (users = []) and then return it after the block (users). — Cary Swoveland
– Cary Swoveland, Commented Nov 18, 2015 at 4:53

AmitA · Accepted Answer · 2015-11-17 21:01:25Z

4

You can use the map method:

users = employees_to_import.map do |employee|
  User.new(employee.slice(:first_name, :last_name, :email))
end

It is also aliased as collect.

From the documentation (here):

The map and collect basically return a new array with the results of running block once for every element:

(1..4).map { |i| i*i }      #=> [1, 4, 9, 16]

answered Nov 17, 2015 at 20:58

AmitA

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