定义 has_rich_text 方法时 __FILE__ 和 __LINE__ + 1 的作用是什么？

Question

__FILE__我在Rails中找到了以下代码，但无法弄清楚和 的作用__LINE__ + 1。class_eval有人能解释一下当您定义如下所示的某些方法时它们的用途吗？

def has_rich_text(name)
  class_eval <<-CODE, __FILE__, __LINE__ + 1
    def #{name}
      self.rich_text_#{name} ||= ActionText::RichText.new(name: "#{name}", record: self)
    end

    def #{name}=(body)
      self.#{name}.body = body
    end
  CODE

  has_one :"rich_text_#{name}", -> { where(name: name) }, class_name: "ActionText::RichText", as: :record, inverse_of: :record, dependent: :destroy

  scope :"with_rich_text_#{name}", -> { includes("rich_text_#{name}") }
  scope :"with_rich_text_#{name}_and_embeds", -> { includes("rich_text_#{name}": { embeds_attachments: :blob }) }

  after_save do
    public_send(name).save if public_send(name).changed?
  end
end

Answer 1

错误报告（回溯）也相应改变：

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class Test\n  def self.fun_ok(name)\n    class_eval <<-CODE, __FILE__, __LINE__ + 1\n      def #{name}; raise; end\n    CODE\n  end\n\n  def self.fun_ko(name)\n    class_eval <<-CODE\n      def #{name}; raise; end\n    CODE\n  end\nend\n

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让\xe2\x80\x99s 创建方法：

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Test.fun_ok("ok")\nTest.fun_ko("ko")\n

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让\xe2\x80\x99s测试：

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begin\n  Test.new.ok\nrescue => e\n  puts e.backtrace.inspect\nend\n#\xe2\x87\x92\xc2\xa0["/tmp/foo.rb:4:in `ok\'", "/tmp/foo.rb:19:in `<main>\'"]\n\nbegin\n  Test.new.ko\nrescue => e\n  puts e.backtrace.inspect\nend\n#\xe2\x87\x92 ["(eval):1:in `ko\'", "/tmp/foo.rb:25:in `<main>\'"]\n

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正如您所看到的，前一个回溯指向源代码中导致异常的确切行（特别是："/tmp/foo.rb:4"部分）。后一个回溯指向任何地方。

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