Question

我确实有以下代码结构：

class Asset < ActiveRecord::Base
  belongs_to :state
  scope :order_by_year, -> { joins(:state).merge(State.order_by_year) }
  ...

class State < ActiveRecord::Base
  belongs_to :financial_statement
  has_many :assets
  scope :order_by_year, -> { joins(:financial_statement).merge(FinancialStatement.order_by_year) }
  ...  

class FinancialStatement < ActiveRecord::Base
  belongs_to :financial_year
  has_many :states
  scope :order_by_year, -> { joins(:financial_year).merge(FinancialYear.order_by_year) }
  ...

class FinancialYear < ActiveRecord::Base
  has_many :financial_statements
  scope :order_by_year, -> { order("financial_years.year DESC") }
  ...

我希望能够像这样调用资产模型：

Asset.order_by_year

我正在尝试遵循Demeter法，因此资产模型不应该知道FinancialYear（其中包含年份信息）。我正在尝试使用merge来实现这一目标。

Asset.order_by_year creates the following sql:

1: SELECT `assets`.* FROM `assets` 
2: INNER JOIN `states` ON `states`.`id` = `assets`.`state_id` 
3: LEFT OUTER JOIN `financial_years` ON `financial_years`.`id` = `financial_statements`.`financial_year_id` 
4: LEFT OUTER JOIN `financial_statements` ON `financial_statements`.`id` = `states`.`financial_statement_id`  
5: ORDER BY financial_years.year DESC

这会出现错误消息，因为第3行和第4行的顺序错误。知道为什么Rails会以这种方式创建查询吗？知道如何更改此结构以使其工作吗？任何帮助将不胜感激。

如何正确使用Rails 4中的合并操作？

0 个答案: