rails之外的cattr_accessor

Question

我正在尝试使用google_search ruby库(代码如下)，但它抱怨“cattr_accessor是一个未定义的方法”--你知道为什么会这样吗?或者我该如何修复它？

require 'rubygems'
require 'google_search'

GoogleSearch.web :q => "pink floyd"

Answer 1

cattr_accessor似乎是一个Rails扩展that acts like attr_accessor, but is accessible on both the class and its instances。

如果您想复制cattr_accessor方法的源代码，请查看this documentation

# File vendor/rails/activesupport/lib/active_support/core_ext/class/attribute_accessors.rb, line 46
def cattr_accessor(*syms)
  cattr_reader(*syms)
  cattr_writer(*syms)
end

# File vendor/rails/activesupport/lib/active_support/core_ext/class/attribute_accessors.rb, line 4
def cattr_reader(*syms)
  syms.flatten.each do |sym|
    next if sym.is_a?(Hash)
    class_eval("unless defined? @@\#{sym}\n@@\#{sym} = nil\nend\n\ndef self.\#{sym}\n@@\#{sym}\nend\n\ndef \#{sym}\n@@\#{sym}\nend\n", __FILE__, __LINE__)
  end
end

# File vendor/rails/activesupport/lib/active_support/core_ext/class/attribute_accessors.rb, line 24
def cattr_writer(*syms)
  options = syms.extract_options!
  syms.flatten.each do |sym|
    class_eval("unless defined? @@\#{sym}\n@@\#{sym} = nil\nend\n\ndef self.\#{sym}=(obj)\n@@\#{sym} = obj\nend\n\n\#{\"\ndef \#{sym}=(obj)\n@@\#{sym} = obj\nend\n\" unless options[:instance_writer] == false }\n", __FILE__, __LINE__)
  end
end

Answer 2

您可以通过包含Ruby Facets gem来获得此功能。请在此处引用源代码：

https://github.com/rubyworks/facets/blob/master/lib/core/facets/cattr.rb

您通常不需要来自gem的所有代码。您可以有选择地请求您想要的内容。不过，gem中有相当多有用的扩展。