Mark dangerous Ruby methods!

Methods that perform a permanent change to the object itself are potentially dangerous. That is why those methods should be marked with an exclamation mark at the end.

For example:

class BankAccount
  attr_accessor :amount
  def initialize amount
    @amount = amount
  end

  def withdraw_money amount
    @amount -= amount
  end
end

should be refactored to:

class BankAccount
  attr_accessor :amount
  def initialize amount
    @amount = amount
  end

  def withdraw_money! amount
    @amount -= amount
  end
end

and using it makes definitely clear, that the money is withdrawn permanently:

bank_account = BankAccount.new 1000
bank_account.withdraw_money! 200
=> 800
person.amount
=> 800

Supported by Ruby 2.1.1