Question

我正在尝试在我的Rails应用程序中的hstore列上创建一个范围。 Product是一个模型，features是hstore类型的属性（使用Postgresql 9.2）。我的范围类定义如下：

class Product < ActiveRecord::Base
    scope :with_features, lambda {|features| where("foo_id in (?)", features)

以上范围仅在您将单个值作为要素传递时才有效。数组抛出错误。这说明如下：

Product.with_features('api')
  => [#<Product id: 1, name: "Sample">] 
     # so great success

# now with an array
Product.with_features(['api','mobile'])
  => ActiveRecord::StatementInvalid: PG::Error: ERROR:  argument of WHERE must be type boolean, not type record 
    # so no good, this query will work as usual if features isn't of type hstore

在Rails 3.2中，似乎支持postgres hstore类型在涉及数组时是有限的（我正在使用https://github.com/softa/activerecord-postgres-hstore）。我一直在尝试使用每个循环的一些解决方案将AND查询附加在一起，而不是运气。有什么想法吗？

Answer 1

我提出的一个解决方案效果很好：

scope :with_features, lambda { |features| 

  #store the composed scope in local variable to build on
  composed_scope = self.scoped

  # if array, then loop through each
  if features.instance_of?(Array)
    features.each do |feature|
      composed_scope = composed_scope.where("features ? :key", :key => feature)
    end

  # otherwise, it's a single string parameter, parse as normal
  else
    composed_scope = composed_scope.where("features ? :key", :key => features)
  end

  # return the newly built composed scope
  composed_scope
}

现在，上述两个示例查询都会返回预期结果。

将数组或参数传递给Rails中的hstore范围时出错

1 个答案: