Question

当我使用我在模型中准备的范围时，rails返回不正确的数据。

我的模特：

class CurrencyRate < ActiveRecord::Base
    scope :eur_today, -> {where(currency: "eur").where(date: Time.now.in_time_zone.to_date).first}
end

来自rails控制台的信息：

2.3.0 :011 > CurrencyRate.eur_today

CurrencyRate Load (0.2ms)  SELECT  "currency_rates".* FROM 
"currency_rates" WHERE "currency_rates"."currency" = ? AND 
"currency_rates"."date" = ?  ORDER BY "currency_rates"."id" ASC LIMIT 1  
[["currency", "eur"], ["date", "2017-08-09"]]
CurrencyRate Load (0.2ms)  SELECT "currency_rates".* FROM 
"currency_rates"

 => #<ActiveRecord::Relation [#<CurrencyRate id: 2, currency: "eur", 
 sale: 4.248546249999998, purchase: 4.265333125, date: "2017-08-08", 
 created_at: "2017-08-08 20:52:08", updated_at: "2017-08-08 20:54:10", 
 sale_percentage_diff: nil, purchase_percentage_diff: nil>]>

当我在范围内使用相同的查询时，返回的数据是正确的：

2.3.0 :012 > CurrencyRate.where(currency: "eur").where(date: Time.now.in_time_zone.to_date).first 

CurrencyRate Load (0.2ms)  SELECT  "currency_rates".* FROM 
"currency_rates" WHERE "currency_rates"."currency" = ? AND 
"currency_rates"."date" = ?  ORDER BY "currency_rates"."id" ASC LIMIT 1  
[["currency", "eur"], ["date", "2017-08-09"]]

=> nil

为什么范围不正确？

Answer 1

因为范围必须返回ActiveRecord::Relation。摆脱范围内的first调用，并在范围之外使用它。为什么？因为范围必须是可链接的。

Rails范围不会返回正确的数据

1 个答案: