无法在Rails中查询hstore属性

Question

我已经添加了一个hstore属性到我的模型:

class ChangePerDayAverageInterestToHstore < ActiveRecord::Migration
  def change
      add_column :companies, :per_day_average_interest, :hstore
  end
end

现在，当我通过控制台生成项目时，我能够毫无问题地查询它。像这样:

irb(main):002:0> t = Company.new per_day_average_interest: {1 => 10, 2 => 3}
irb(main):011:0> t.per_day_average_interest 
=> {"1"=>"10", "2"=>"3"}
irb(main):013:0> t.per_day_average_interest["1"]                                                                                  => "10"
irb(main):014:0> t.per_day_average_interest["2"]
=> "3" 

当我保存它，然后查询它，我得到一个No Method错误:

irb(main):028:0> t.save!
(0.2ms)  BEGIN                                                                                                                  SQL (0.3ms)  INSERT INTO "companies" ("created_at", "per_day_average_interest", "updated_at") VALUES ($1, $2, $3) RETURNING "id"  [["created_at", "2015-06-08 19:24:39.694533"], ["per_day_average_interest", ""1"=>"10","2"=>"3""], ["updated_at", "2015-06-08 19:24:39.694533"]]
(21.4ms)  COMMIT                                                                                                                
=> true 
irb(main):029:0> d = Company.where(:id => 44)
  Company Load (0.5ms)  SELECT "companies".* FROM "companies"  WHERE "companies"."id" = 44
=> #<ActiveRecord::Relation [#<Company id: 44, name: nil, average: nil, created_at: "2015-06-08 19:24:39", updated_at: "2015-06-08 19:24:39", revenue_average: nil, country: nil, job: nil, model_name:
 nil, average_daily_interest: nil, per_day_average_interest: {"1"=>"10", "2"=>"3"}>]>
irb(main):030:0> d.per_day_average_interest
NoMethodError: undefined method `per_day_average_interest' for #<Company::ActiveRecord_Relation:0x007fa16d296dd0>
from /home/action/.gem/ruby/2.1.1/gems/activerecord-4.1.0/lib/active_record/relation/delegation.rb:136:in `method_missing'      
from /home/action/.gem/ruby/2.1.1/gems/activerecord-4.1.0/lib/active_record/relation/delegation.rb:99:in `method_missing'       
from (irb):30
from /home/action/.gem/ruby/2.1.1/gems/railties-4.1.0/lib/rails/commands/console.rb:90:in `start'                                                                                              
        from /home/action/.gem/ruby/2.1.1/gems/railties-4.1.0/lib/rails/commands/console.rb:9:in `start'                                                                                               
        from /home/action/.gem/ruby/2.1.1/gems/railties-4.1.0/lib/rails/commands/commands_tasks.rb:69:in `console'                                                                                     
        from /home/action/.gem/ruby/2.1.1/gems/railties-4.1.0/lib/rails/commands/commands_tasks.rb:40:in `run_command!'                                                                                
        from /home/action/.gem/ruby/2.1.1/gems/railties-4.1.0/lib/rails/commands.rb:17:in `<top (required)>'                                                                                           
        from bin/rails:4:in `require'                                                                                                                                                                  
        from bin/rails:4:in `<main>' 

我的查询方式是否错误?我是不是漏掉了什么?

谢谢!

Answer 1

where语句返回对象集合，您的列属于一个对象，因此您需要执行以下操作d = Company.where(:id => 44).first

Answer 2

可以看到，d是ActiveRecord::Relation对象，它是使用where过滤后的所有Company对象的包装。读取器方法per_day_average_interest是在Company模型实例上定义的，因此您需要像下面所示的那样调用。

d.first.per_day_average_interest

如果你想要所有的值d.pluck(:per_day_average_interest) .