class RuboCop::Cop::Rails::Pluck

This cop enforces the use of `pluck` over `map`.

`pluck` can be used instead of `map` to extract a single key from each element in an enumerable. When called on an Active Record relation, it results in a more efficient query that only selects the necessary key.

@example

# bad
Post.published.map { |post| post[:title] }
[{ a: :b, c: :d }].collect { |el| el[:a] }

# good
Post.published.pluck(:title)
[{ a: :b, c: :d }].pluck(:a)

Constants

MSG

Public Instance Methods

on_block(node) click to toggle source
# File lib/rubocop/cop/rails/pluck.rb, line 32
def on_block(node)
  pluck_candidate?(node) do |method, argument, element, value|
    next unless argument == element

    message = message(method, argument, element, value)

    add_offense(offense_range(node), message: message) do |corrector|
      corrector.replace(offense_range(node), "pluck(:#{value})")
    end
  end
end

Private Instance Methods

message(method, argument, element, value) click to toggle source
# File lib/rubocop/cop/rails/pluck.rb, line 50
def message(method, argument, element, value)
  format(MSG, method: method, argument: argument, element: element, value: value)
end
offense_range(node) click to toggle source
# File lib/rubocop/cop/rails/pluck.rb, line 46
def offense_range(node)
  node.send_node.loc.selector.join(node.loc.end)
end