class RuboCop::Cop::Rails::Pluck

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

}
Post.published.map { |post| post }
# bad
@example
results in a more efficient query that only selects the necessary key.
element in an enumerable. When called on an Active Record relation, it
`pluck` can be used instead of ‘map` to extract a single key from each
This cop enforces the use of `pluck` over `map`.

def message(method, argument, element, value) 

def message(method, argument, element, value)
  format(MSG, method: method, argument: argument, element: element, value: value)
end

def offense_range(node) 

def offense_range(node)
  node.send_node.loc.selector.join(node.loc.end)
end

def on_block(node) 

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