class RuboCop::Cop::Style::UnpackFirst


‘foo’.unpack1(‘h*’)
# good

’foo’.unpack(‘h*’).at(0)
‘foo’.unpack(‘h*’).slice(0)
‘foo’.unpack(‘h*’)[0]
‘foo’.unpack(‘h*’).first
# bad
@example
which can be replaced with the shorter method ‘unpack1`.
This cop checks for accessing the first element of `String#unpack`

def first_element_range(node, unpack_call) 

def first_element_range(node, unpack_call)
  Parser::Source::Range.new(node.loc.expression.source_buffer,
                            unpack_call.loc.expression.end_pos,
                            node.loc.expression.end_pos)
end

def on_send(node) 

def on_send(node)
  unpack_and_first_element?(node) do |unpack_call, unpack_arg|
    range = first_element_range(node, unpack_call)
    message = format(MSG,
                     receiver: unpack_call.receiver.source,
                     format: unpack_arg.source,
                     method: range.source)
    add_offense(node, message: message) do |corrector|
      corrector.remove(first_element_range(node, unpack_call))
      corrector.replace(unpack_call.loc.selector, 'unpack1')
    end
  end
end