Question

我希望能够在我的代码中使用以下构造：

p obj.graph_XYZ
obj.graph_XYZ << obj2

在这里，我想处理以graph_

开头的任何getter / setter

我可以挂钩到getter，但是即使我使用obj.graph_XYZ << obj2，method_missing也会选择getter。关于我可能做错的任何输入？

Answer 1

这样的事可能对你有用吗？

$ irb                                                                                      

class A
  attr_accessor :xyz
end
=> nil
a = A.new
=> #<A:0x0000010096bc88>
a.xyz
=> nil
a.xyz << 2
NoMethodError: undefined method `<<' for nil:NilClass
  from (irb):6
  from /Users/iain/.rvm/rubies/ruby-1.9.2-p290/bin/irb:16:in `<main>'
a.xyz = [ ]
=> []
a.xyz << 2
=> [2]
a.xyz
=> [2]
class A
  def method_missing( name, *args )
    return super( name, *args ) unless name.to_s =~ /^graph/  
    words = name.to_s.split( "_" )
    words.shift # get rid of graph_

    # now do what you like
    # ...
    if (instance_variable_get "@#{words.first.downcase}").nil?
      instance_variable_set "@#{words.first.downcase}", []
    end

    (instance_variable_get "@#{words.first.downcase}")
  end
end
=> nil
a = A.new
=> #<A:0x00000100844a58>
a.graph_XYZ
=> []
a.graph_XYZ << 2
=> [2]
a.graph_XYZ
=> [2]

使用method_missing定义动态setter

1 个答案: