ruby - 通过 Ruby 元编程调用实例方法而不指定实例？

Question

如何设计scope方法让它真正放入row.city？

row.scope do 
  puts city
end

Answer 1

使用instance_eval:

class RowClass
  attr_accessor :city

  def scope(&blk)
    instance_eval(&blk)
  end
end

row = RowClass.new
row.city = "bla"

row.scope do 
  puts city # prints "bla"
end