`initialize'：错误的参数个数（1表示0）

I'm getting an error with the following example when running the program.

我在运行程序时遇到以下示例的错误。

The error reads as such:

错误如下：

burger.rb:8:in `initialize': wrong number of arguments (1 for 0) (ArgumentError)
    from burger.rb:19:in `new'
    from burger.rb:19:in `<main>'

Any help is appreciated for this noob, the code is below:

这个菜鸟的任何帮助表示赞赏，代码如下：

$toppings = false

class Burger
    AVAILABLE_TOPPINGS = ["lettuce", "tomato", "onion", "cheese"]

    attr_reader :options

    def initialize
        @toppings = []
    end

    def order
        print "how many burgers would you like? "
        number = gets.chomp
        puts "#{number} burgers coming right up boss!"
    end
end

burger = Burger.new("lettuce")

burger.order

3 个解决方案

#1

As others have said your initializer is expecting no arguments but you're giving it lettuce. If you're using ruby 2.1 or later I would suggest using keyword arguments:

正如其他人所说的那样，你的初始化者不会有任何争论，但是你会给它生菜。如果您使用ruby 2.1或更高版本，我建议使用关键字参数：

class Burger
  TOPPINGS = %i[lettuce tomato onion cheese]

  attr_reader :toppings

  def initialize(toppings: [])
    @toppings = TOPPINGS & toppings
  end
end

This allows you do to Burger.new(toppings: [:lettuce]) which I feel is a lot more readable.

这允许你做Burger.new（浇头：[：生菜]），我觉得它更具可读性。

#2

The error is telling you that the method initialize expects 0 argument, while you give it 1 ("lettuce" in Burger.new("lettuce")).

错误告诉你方法initialize需要0参数，而你给它1（Burger.new（“生菜”）中的“生菜”）。

You need to make initialize expecting one argument:

你需要初始化期望一个参数：

def initialize(options)
    @toppings = []
    @options = options
end

#3

$toppings = false

is code smell. Globals are generally not necessary, and should only be used when you're absolutely sure they're needed. When you're first learning an OO language I think it's better to avoid them and learn about variable scoping.

是代码味道。全局通常不是必需的，只有在您完全确定需要它们时才应使用。当你第一次学习OO语言时，我认为最好避免它们并学习变量范围。

In this case, you don't use it in your sample code, but you do use:

在这种情况下，您不要在示例代码中使用它，但您确实使用：

@toppings = []

(which is again not used elsewhere). It isn't a good idea to name a global variable the same as an instance variable because it's too easy to use one when you mean the other, and introduce a bug.

（这在其他地方也没有使用过）。将全局变量命名为与实例变量相同并不是一个好主意，因为当你的意思是另一个时，它太容易使用了一个，并引入了一个bug。

#1