Class: RuboCop::Cop::Performance::ReverseFirst

Relationships & Source Files
Super Chains via Extension / Inclusion / Inheritance
Class Chain: self, AutoCorrector, Base
Instance Chain: self, RangeHelp, Base
Inherits:	Base Object Base RuboCop::Cop::Performance::ReverseFirst
Defined in:	lib/rubocop/cop/performance/reverse_first.rb

Overview

Identifies places where reverse.first(n) and reverse.first can be replaced by last(n).reverse and last.

Examples:

# bad
array.reverse.first(5)
array.reverse.first

# good
array.last(5).reverse
array.last

Constant Summary

MSG =
# File 'lib/rubocop/cop/performance/reverse_first.rb', line 23
```
'Use `%<good_method>s` instead of `%<bad_method>s`.'
```
RESTRICT_ON_SEND =
# File 'lib/rubocop/cop/performance/reverse_first.rb', line 24
```
%i[first].freeze
```

Instance Method Summary

#on_csend(node)

Alias for #on_send.
#on_send(node) (also: #on_csend)
#build_good_method(node) private
#build_message(node, range) private
#correction_range(receiver, node) private

Instance Method Details

#build_good_method(node) (private)

[ GitHub ]

# File 'lib/rubocop/cop/performance/reverse_first.rb', line 56


def build_good_method(node)
  if node.arguments?
    "last(#{node.first_argument.source})#{node.loc.dot.source}reverse"
  else
    'last'
  end
end

#build_message(node, range) (private)

[ GitHub ]

# File 'lib/rubocop/cop/performance/reverse_first.rb', line 50


def build_message(node, range)
  good_method = build_good_method(node)
  bad_method = range.source
  format(MSG, good_method: good_method, bad_method: bad_method)
end

#correction_range(receiver, node) (private)

[ GitHub ]

# File 'lib/rubocop/cop/performance/reverse_first.rb', line 46


def correction_range(receiver, node)
  range_between(receiver.loc.selector.begin_pos, node.source_range.end_pos)
end

#on_csend(node)

Alias for #on_send.

[ GitHub ]

# File 'lib/rubocop/cop/performance/reverse_first.rb', line 42


alias on_csend on_send

#on_send(node) Also known as: #on_csend

[ GitHub ]

# File 'lib/rubocop/cop/performance/reverse_first.rb', line 30


def on_send(node)
  reverse_first_candidate?(node) do |receiver|
    range = correction_range(receiver, node)
    message = build_message(node, range)

    add_offense(range, message: message) do |corrector|
      replacement = build_good_method(node)

      corrector.replace(range, replacement)
    end
  end
end