Question

我正在尝试查询模型中的列：

require 'rubygems'
require 'dm-core'
require 'dm-migrations'
require 'dm-aggregates'

db_name = 'mydb.sqlite'

DataMapper::Logger.new($stdout, :debug)
DataMapper.setup(:default, 'sqlite://' + Dir.pwd + '/' + db_name)

class Context
  include DataMapper::Resource
  property :id,         Serial
  property :order,      Integer

  def initialize
    self.order = (self.class.max(:order) || 0) + 1
  end

  def move_up
    temp = self.class.first(:order => (self.order - 1))
    temp.order += 1
    temp.save
    self.order -= 1
    self.save
  end

end

DataMapper.finalize
DataMapper.auto_upgrade!

但是当我创建几个实例时，我在调用move_up方法时遇到以下错误。

Failure/Error: context2.move_up
+options[:order]+ entry 1 of an unsupported object Fixnum
# ./context.rb:11:in `move_up'

尽管有边缘条件，为什么这不起作用？

Answer 1

：order是保留字，因为它是您传递给查询的选项之一。只需将其重命名为不同的东西，它就会起作用

为什么我不能查询我的DataMapper模型？

1 个答案: