Class: RuboCop::Cop::Performance::CollectionLiteralInLoop

Inherits:
Base
  • Object
show all
Defined in:
lib/rubocop/cop/performance/collection_literal_in_loop.rb

Overview

Identifies places where Array and Hash literals are used within loops. It is better to extract them into a local variable or constant to avoid unnecessary allocations on each iteration.

You can set the minimum number of elements to consider an offense with ‘MinSize`.

Examples:

# bad
users.select do |user|
  %i[superadmin admin].include?(user.role)
end

# good
admin_roles = %i[superadmin admin]
users.select do |user|
  admin_roles.include?(user.role)
end

# good
ADMIN_ROLES = %i[superadmin admin]
...
users.select do |user|
  ADMIN_ROLES.include?(user.role)
end

Constant Summary collapse

MSG = 
'Avoid immutable %<literal_class>s literals in loops. ' \
'It is better to extract it into a local variable or a constant.'
POST_CONDITION_LOOP_TYPES = 
%i[while_post until_post].freeze
LOOP_TYPES = 
(POST_CONDITION_LOOP_TYPES + %i[while until for]).freeze
ENUMERABLE_METHOD_NAMES = 
(Enumerable.instance_methods + [:each]).to_set.freeze
NONMUTATING_ARRAY_METHODS = 
%i[& * + - <=> == [] all? any? assoc at
bsearch bsearch_index collect combination
compact count cycle deconstruct difference dig
drop drop_while each each_index empty? eql?
fetch filter find_index first flatten hash
include? index inspect intersection join
last length map max min minmax none? one? pack
permutation product rassoc reject
repeated_combination repeated_permutation reverse
reverse_each rindex rotate sample select shuffle
size slice sort sum take take_while
to_a to_ary to_h to_s transpose union uniq
values_at zip |].freeze
ARRAY_METHODS = 
(ENUMERABLE_METHOD_NAMES | NONMUTATING_ARRAY_METHODS).to_set.freeze
NONMUTATING_HASH_METHODS = 
%i[< <= == > >= [] any? assoc compact dig
each each_key each_pair each_value empty?
eql? fetch fetch_values filter flatten has_key?
has_value? hash include? inspect invert key key?
keys? length member? merge rassoc rehash reject
select size slice to_a to_h to_hash to_proc to_s
transform_keys transform_values value? values values_at].freeze
HASH_METHODS = 
(ENUMERABLE_METHOD_NAMES | NONMUTATING_HASH_METHODS).to_set.freeze

Instance Method Summary collapse

Instance Method Details

#on_send(node) ⇒ Object 



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# File 'lib/rubocop/cop/performance/collection_literal_in_loop.rb', line 80

def on_send(node)
  receiver, method, = *node.children
  return unless check_literal?(receiver, method) && parent_is_loop?(receiver)

  message = format(MSG, literal_class: literal_class(receiver))
  add_offense(receiver, message: message)
end