Question

如果rails中不存在某个方法，我正在尝试返回一些内容。

我看起来像这样的红宝石模型：

class myModel

  attr_accessible :attr_a, :attr_b, #name of attributes `attr_c` and `attr_d`
                  :attr_c, :attr_d  #are equal to `method_c` and `method_d` names
  #init some values
  after_initialize :default_values

  def default_values
    self.is_active ||= true
    self.attr_a ||= 'None'
    self.attr_b ||= 1
    if !self.respond_to?("method_c")
      #return something if the method is called
      self.method_c = 'None' #not working
    end
    if !self.respond_to?("method_d")
      #return something if the method is called
      self.method_d = 'None' #not working
    end
  end

  #more methods
end

但是我的规范测试中出现错误：

   NoMethodError:
     undefined method `method_c' for #<Object:0xbb9e53c>

我知道这听起来很疯狂但是，如果方法不存在，我该怎么做才能返回？

Answer 1

Ruby有一个名为#method_missing的优秀构造，只要将消息发送到不处理该方法的对象，就会调用它。您可以使用它通过方法名称动态处理方法：

class MyModel

  attr_accessible :attr_a, :attr_b, #name of attributes `attr_c` and `attr_d`
                  :attr_c, :attr_d  #are equal to `method_c` and `method_d` names
  #init some values
  after_initialize :default_values

  def default_values
    self.is_active ||= true
    self.attr_a    ||= 'None'
    self.attr_b    ||= 1
  end

  def method_missing(method, *args)
    case method
    when :method_c
      attr_c = "None"   # Assigns to attr_c and returns "None"
    when :method_d
      attr_d = "None"   # Assigns to attr_d and returns "None"
    else
      super             # If it wasn't handled, then just pass it on, which will result in an exception.
    end
  end
end

Rails对false response_to做出反应？

1 个答案: