Class: RuboCop::Cop::Performance::Count

Inherits:

Cop

• Object
• Cop
• RuboCop::Cop::Performance::Count

Includes:

SafeMode

Defined in:

lib/rubocop/cop/performance/count.rb

Overview

This cop is used to identify usages of count on an Enumerable that follow calls to select or reject. Querying logic can instead be passed to the count call.

ActiveRecord compatibility: ActiveRecord will ignore the block that is passed to count. Other methods, such as select, will convert the association to an array and then run the block on the array. A simple work around to make count work with a block is to call ‘to_a.count …`.

Example:

Model.where(id: [1, 2, 3].select { |m| m.method == true }.size

becomes:

Model.where(id: [1, 2, 3]).to_a.count { |m| m.method == true }

Examples:

# bad
[1, 2, 3].select { |e| e > 2 }.size
[1, 2, 3].reject { |e| e > 2 }.size
[1, 2, 3].select { |e| e > 2 }.length
[1, 2, 3].reject { |e| e > 2 }.length
[1, 2, 3].select { |e| e > 2 }.count { |e| e.odd? }
[1, 2, 3].reject { |e| e > 2 }.count { |e| e.even? }
array.select(&:value).count

# good
[1, 2, 3].count { |e| e > 2 }
[1, 2, 3].count { |e| e < 2 }
[1, 2, 3].count { |e| e > 2 && e.odd? }
[1, 2, 3].count { |e| e < 2 && e.even? }
Model.select('field AS field_one').count
Model.select(:value).count

Constant Summary

MSG =

'Use `count` instead of `%s...%s`.'.freeze

SELECTORS =

[:reject, :select].freeze

COUNTERS =

[:count, :length, :size].freeze

Constants included from Util

Util::ASGN_NODES, Util::BYTE_ORDER_MARK, Util::EQUALS_ASGN_NODES, Util::LITERAL_REGEX, Util::OPERATOR_METHODS, Util::SHORTHAND_ASGN_NODES

Instance Attribute Summary

Attributes inherited from Cop

#config, #corrections, #offenses, #processed_source

Instance Method Summary

• #on_send(node) ⇒ Object

Methods inherited from Cop

#add_offense, all, #config_to_allow_offenses, #config_to_allow_offenses=, #cop_config, cop_name, #cop_name, cop_type, #correct, #debug?, #details, #display_cop_names?, #display_style_guide?, #duplicate_location?, #excluded_file?, #extra_details?, #find_location, #highlights, inherited, #initialize, #join_force?, lint?, match?, #message, #messages, non_rails, qualified_cop_name, #reference_url, #relevant_file?, #style_guide_url, #target_ruby_version

Methods included from Sexp

#s

Methods included from NodePattern::Macros

#def_node_matcher, #def_node_search, #node_search, #node_search_all, #node_search_body, #node_search_first

Methods included from AutocorrectLogic

#autocorrect?, #autocorrect_enabled?, #autocorrect_requested?, #support_autocorrect?

Methods included from IgnoredNode

#ignore_node, #ignored_node?, #part_of_ignored_node?

Methods included from Util

begins_its_line?, block_length, comment_line?, compatible_external_encoding_for?, directions, double_quotes_acceptable?, double_quotes_required?, effective_column, ends_its_line?, escape_string, first_part_of_call_chain, hard_to_type?, interpret_string_escapes, line_distance, line_range, move_pos, needs_escaping?, numeric_range_size, on_node, operator?, parentheses?, parenthesized_call?, preceed?, range_between, range_with_surrounding_comma, range_with_surrounding_space, same_line?, source_range, strip_quotes, stripped_source_upto, to_string_literal, to_symbol_literal, within_node?

Methods included from PathUtil

absolute?, match_path?, relative_path

Constructor Details

This class inherits a constructor from RuboCop::Cop::Cop

Instance Method Details

#on_send(node) ⇒ Object

# File 'lib/rubocop/cop/performance/count.rb', line 48

def on_send(node)
  return if rails_safe_mode?

  @selector, @selector_loc, @params, @counter = parse(node)

  check(node)
end