Rails 3.2 - 未定义的方法`where'for#<Array:... - Model.where()的查询

Question

我试图将给定的Header字段与Alarm模型中的其他字段进行比较.正如您在代码中看到的,我在3个不同的步骤中过滤警报.前2个工作完美.但是,最后一个不起作用.它说:

undefined method `where' for #<Array:...

据我所知,.where是一个适用于数组的类方法.为什么不在这里工作？我也尝试了.find_all_by不同的东西......但无济于事.

@header = Header.find(1)

# Extracts those alarms that are ACTIVE and have something in common with the tittles
@alarmsT = Alarm.activated.where("keyword in (?)", [@header.title_es, @header.title_en, @header.title_en])

# Extracts alarms when Header has at least the same categories as an alarm
@alarmsT = @alarmsT.select do |alarm| 
   @header.category_ids.all?{|c| alarm.category_ids.include? c }
end

// this is the one that does NOT work
# Extract alarms which share the same location as Header.events' town
@alarmsF = [] 
@header.events.each do |e|
    @alarmsF =  @alarmsF + @alarmsT.where("alarms.location LIKE ?", e.town)
end

任何帮助发现我错过的东西非常感谢.谢谢

Answer 1

在第一行中,您成功返回了一个ActiveRecordRelation对象@alarmsT

# Extracts those alarms that are ACTIVE and have something in common with the tittles
@alarmsT = Alarm.activated.where("keyword in (?)", [@header.title_es, @header.title_en, @header.title_en])

此时,您可以应用其他.where(...)方法,条件或范围,@alarmsT以进一步构建ARel表达式并返回结果.

但是,然后在此关系上运行过滤器,转换@alarmsT为实例Array

# Extracts alarms when Header has at least the same categories as an alarm
@alarmsT = @alarmsT.select do |alarm| 
   @header.category_ids.all?{|c| alarm.category_ids.include? c }
end

您无法再构建ARel表达式,因为Array您不了解您的ARel .where(...)方法或任何Alarm模型的范围或属性.这就是为什么在下面的代码中你得到undefined method 'where' for #<Array:...错误 - 你正在调用.where()一个实例Array; 一种不存在的方法.

@alarmsF = [] 
@header.events.each do |e|
  @alarmsF =  @alarmsF + @alarmsT.where("alarms.location LIKE ?", e.town)
end

您可以通过不按类别ID进行过滤而使用连接来解决此问题.构建这样的连接(以验证相关表/列中至少存在一个值的子集)在很容易通过谷歌和StackOverflow找到的地方记录.