class RuboCop::Cop::Style::CombinableLoops

Checks for places where multiple consecutive loops over the same data can be combined into a single loop. It is very likely that combining them will make the code more efficient and more concise.

@safety

The cop is unsafe, because the first loop might modify state that the
second loop depends on; these two aren't combinable.

@example

# bad
def method
  items.each do |item|
    do_something(item)
  end

  items.each do |item|
    do_something_else(item)
  end
end

# good
def method
  items.each do |item|
    do_something(item)
    do_something_else(item)
  end
end

# bad
def method
  for item in items do
    do_something(item)
  end

  for item in items do
    do_something_else(item)
  end
end

# good
def method
  for item in items do
    do_something(item)
    do_something_else(item)
  end
end

# good
def method
  each_slice(2) { |slice| do_something(slice) }
  each_slice(3) { |slice| do_something(slice) }
end

Constants

MSG

Public Instance Methods

on_block(node) click to toggle source

# File lib/rubocop/cop/style/combinable_loops.rb, line 66
def on_block(node)
  return unless node.parent&.begin_type?
  return unless collection_looping_method?(node)
  return unless same_collection_looping_block?(node, node.left_sibling)
  return unless node.body && node.left_sibling.body

  add_offense(node) do |corrector|
    combine_with_left_sibling(corrector, node)
  end
end

Also aliased as: on_numblock

on_for(node) click to toggle source

# File lib/rubocop/cop/style/combinable_loops.rb, line 79
def on_for(node)
  return unless node.parent&.begin_type?
  return unless same_collection_looping_for?(node, node.left_sibling)

  add_offense(node) do |corrector|
    combine_with_left_sibling(corrector, node)
  end
end

on_numblock(node)

Alias for: on_block

Private Instance Methods

collection_looping_method?(node) click to toggle source

# File lib/rubocop/cop/style/combinable_loops.rb, line 90
def collection_looping_method?(node)
  method_name = node.method_name
  method_name.start_with?('each') || method_name.end_with?('_each')
end

combine_with_left_sibling(corrector, node) click to toggle source

# File lib/rubocop/cop/style/combinable_loops.rb, line 106
def combine_with_left_sibling(corrector, node)
  corrector.replace(
    node.left_sibling.body,
    "#{node.left_sibling.body.source}\n#{node.body.source}"
  )
  corrector.remove(range_with_surrounding_space(range: node.source_range, side: :left))
end

same_collection_looping_block?(node, sibling) click to toggle source

# File lib/rubocop/cop/style/combinable_loops.rb, line 95
def same_collection_looping_block?(node, sibling)
  (sibling&.block_type? || sibling&.numblock_type?) &&
    sibling.send_node.method?(node.method_name) &&
    sibling.receiver == node.receiver &&
    sibling.send_node.arguments == node.send_node.arguments
end

same_collection_looping_for?(node, sibling) click to toggle source

# File lib/rubocop/cop/style/combinable_loops.rb, line 102
def same_collection_looping_for?(node, sibling)
  sibling&.for_type? && node.collection == sibling.collection
end