Class: RuboCop::Cop::Rails::Pluck

Inherits:
Base
  • Object
show all
Extended by:
AutoCorrector, TargetRailsVersion
Defined in:
lib/rubocop/cop/rails/pluck.rb

Overview

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.

Examples:

# 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)

Cop Safety Information:

  • This cop is unsafe because model can use column aliases.

    [source,ruby]

    Original code

    User.select('name AS nickname').map { |user| user[:nickname] } # => array of nicknames

    After autocorrection

    User.select('name AS nickname').pluck(:nickname) # => raises ActiveRecord::StatementInvalid

Constant Summary collapse

MSG = 
'Prefer `%<replacement>s` over `%<current>s`.'

Constants included from TargetRailsVersion

TargetRailsVersion::USES_REQUIRES_GEM_API

Instance Method Summary collapse

Methods included from TargetRailsVersion

minimum_target_rails_version, support_target_rails_version?

Instance Method Details

#on_block(node) ⇒ Object Also known as: on_numblock 



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# File 'lib/rubocop/cop/rails/pluck.rb', line 44

def on_block(node)
  pluck_candidate?(node) do |argument, key|
    next if key.regexp_type? || !use_one_block_argument?(argument)

    match = if node.block_type?
              block_argument = argument.children.first.source
              use_block_argument_in_key?(block_argument, key)
            else # numblock
              argument == 1 && use_block_argument_in_key?('_1', key)
            end
    next unless match

    register_offense(node, key)
  end
end