123456789_123456789_123456789_123456789_123456789_

Class: RuboCop::Cop::Performance::MapMethodChain

Relationships & Source Files
Super Chains via Extension / Inclusion / Inheritance
Class Chain:
self, Base
Instance Chain:
self, IgnoredNode, Base
Inherits: Base
  • Object
Defined in: lib/rubocop/cop/performance/map_method_chain.rb

Overview

Checks if the map method is used in a chain.

Autocorrection is not supported because an appropriate block variable name cannot be determined automatically.

class X
  def initialize
    @@num = 0
  end

  def foo
    @@num += 1
    self
  end

  def bar
    @@num * 2
  end
end

[X.new, X.new].map(&:foo).map(&:bar) # => [4, 4]
[X.new, X.new].map { |x| x.foo.bar } # => [2, 4]

Examples:

# bad
array.map(&:foo).map(&:bar)

# good
array.map { |item| item.foo.bar }

Cop Safety Information:

  • This cop is unsafe because false positives occur if the number of times the first method is executed affects the return value of subsequent methods.

Constant Summary

Instance Method Summary

Instance Method Details

#find_begin_of_chained_map_method(node, map_args) (private)

[ GitHub ] 

  


# File 'lib/rubocop/cop/performance/map_method_chain.rb', line 72



def find_begin_of_chained_map_method(node, map_args)
  return unless (chained_map_method = node.receiver)
  return if !chained_map_method.call_type? || !RESTRICT_ON_SEND.include?(chained_map_method.method_name)
  return unless (map_arg = block_pass_with_symbol_arg?(chained_map_method.first_argument))

  map_args.unshift(map_arg)

  receiver = chained_map_method.receiver

  return chained_map_method unless receiver&.call_type? && block_pass_with_symbol_arg?(receiver.first_argument)

  find_begin_of_chained_map_method(chained_map_method, map_args)
end


  








  

    #on_send(node)  
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/performance/map_method_chain.rb', line 53



def on_send(node)
  return if part_of_ignored_node?(node)
  return unless (map_arg = block_pass_with_symbol_arg?(node.first_argument))

  map_args = [map_arg]

  return unless (begin_of_chained_map_method = find_begin_of_chained_map_method(node, map_args))

  range = begin_of_chained_map_method.loc.selector.begin.join(node.source_range.end)
  message = format(MSG, method_name: begin_of_chained_map_method.method_name, map_args: map_args.join('.'))

  add_offense(range, message: message)

  ignore_node(node)
end