class RuboCop::Cop::Style::VariableName

snake_case or camelCase, for their names.
This cop makes sure that all variables use the configured style,

def message(style) 

def message(style)
  format('Use %s for variable names.', style)
end

def on_cvasgn(node) 

def on_cvasgn(node)
  name, = *node
  check_name(node, name, node.loc.name)
end

def on_ivasgn(node) 

def on_ivasgn(node)
  name, = *node
  check_name(node, name, node.loc.name)
end

def on_lvasgn(node) 

def on_lvasgn(node)
  name, = *node
  check_name(node, name, node.loc.name)
end