如何不仅获取单个记录而且获取属于特定搜索查询的所有记录 [英] How to get not only single record but all records that belong to specific search query

问题描述

我写了这个搜索查询，它只返回一条记录:

 @messages = Message.find_by_sender_username(@user.username)#<消息 ID:1，sender_username:emmanuel"，reciepent_username:elias"，正文:Die erste Nachricht"，gelesen:"，created_at:2013-10-26 11:17:53"，updated_at:2013-10-26 11:17:53">

虽然在我的 Message 模型中，我有两条记录，其 sender_username 为emmanuel"

 #<Message id: 1, sender_username: "emmanuel", reciepent_username: "elias", body: "Die erste Nachricht", gelesen: "", created_at: "2013-10-26 11:17:53", updated_at: "2013-10-26 11:17:53">#<消息ID:2，sender_username:emmanuel"，reciepent_username:vera"，body:Was soll ich dazu sagen"，gelesen:"，created_at:2013-10-26 11:23:57"，更新时间:2013-10-26 11:23:57">

我认为问题在于我在模型之间没有真正的关系:

管理员用户名:字符串

用户用户名:字符串

留言

sender_username:string

reciepent_username:string

正文:字符串

读:布尔值

MyQuestion 是我应该如何编写这些模型之间的关系，我为这种关系提供了一些关于 forgein_key 的信息，但我不是 100% 确定如何使用它！

解决方案

Rails 使用 :

类消息'消息'，如::可发送has_many :received_messages, :class_name =>'消息'，如::可接收结尾类用户'消息'，如::可发送has_many :received_messages, :class_name =>'消息'，如::可接收结尾

我不知道此代码是否开箱即用，但它绝对为您指明了正确的方向.它的工作方式是为您的 foreign_key 提供一个 关联模型，这意味着您可以区分是管理员还是用户发送了消息.

这意味着如果你调用 @messages = @user.received_messages ，ActiveRecord 会自动 ping Message model，并拉出 receiveable_id =user.id AND receiveable_type = User

<小时>

为此，您需要替换您的 sender_username &4 列的接收者用户名:

sendable_id可发送类型可接收ID可接收类型

I wrote this search query, that only returns an single record:

 @messages = Message.find_by_sender_username(@user.username)

 #<Message id: 1, sender_username: "emmanuel", reciepent_username: "elias", body: "Die erste Nachricht", gelesen: "", created_at: "2013-10-26 11:17:53", updated_at: "2013-10-26 11:17:53"> 

Although in my Message model i have two records with the sender_username "emmanuel"

 #<Message id: 1, sender_username: "emmanuel", reciepent_username: "elias", body: "Die erste Nachricht", gelesen: "", created_at: "2013-10-26 11:17:53", updated_at: "2013-10-26 11:17:53"> 
 #<Message id: 2, sender_username: "emmanuel", reciepent_username: "vera", body: "Was soll ich dazu sagen", gelesen: "", created_at: "2013-10-26 11:23:57", updated_at: "2013-10-26 11:23:57">

I think the problem is that i have no real relation between the models:

Admin username:string

User username:string

Message

sender_username:string

reciepent_username:string

body:string

read:boolean

MyQuestion is how i should write a relation between this models, i herad something about forgein_key for such relations but im not 100% sure how to make use of it!

解决方案

Rails uses relational databases through a technology called ActiveRecord. This is a type of SQL which basically allows you to "link" tables through a series of relations:

belongs_to
has_one
has_many
has_many :through
has_one :through
has_and_belongs_to_many

The way you link your tables is dependant on how the relationship is built, but in your case, you'd use something like this:

Ruby on rails - Reference the same model twice?

#app/models/message.rb
has_one :sender, :class_name => 'User', :foreign_key => 'sender_id'
has_one :recipient, :class_name => 'User', :foreign_key => 'recipient_id'


#app/models/user.rb
has_many :sent_messages, :class_name => 'Message', :foreign_key => 'sender_id'
has_many :received_messages, :class_name => 'Message', :foreign_key => 'recipient_id'

---

You'll have to edit your tables to have a foreign key column for each relation. You've kind-of done this already, but you need to know that a foreign key is always an ID. So instead of sender_username, you'd have sender_id

This is because the primary key is always a unique ID, which means that ID can be used to identify the record's associations in other tables; meaning you'll be able to reference the record in any query you perform

---

This will allow you to do this:

@messages = @user.received_messages

Instead of having to mess around with 100's of different queries

---

Update

If you want to include Admin messages into the mix, you'd want to include a polymorphic association:

class Message < ActiveRecord::Base
  belongs_to :sendable, polymorphic: true
  belongs_to :receiveable, polymorphic: true
end

class Admin < ActiveRecord::Base
  has_many :sent_messages, :class_name => 'Message', as: :sendable
  has_many :received_messages, :class_name => 'Message', as: :receiveable
end

class User < ActiveRecord::Base
  has_many :sent_messages, :class_name => 'Message', as: :sendable
  has_many :received_messages, :class_name => 'Message', as: :receiveable
end

I don't know if this code will work out of the box, but it is definitely point you in the right direction. The way it works is to give your foreign_key an associated model, which means that you can differentiate between whether an admin or user sent the message.

This means that if you call @messages = @user.received_messages , ActiveRecord will automatically ping the Message model, and pull out the rows where receiveable_id = user.id AND receiveable_type = User

---

For this to work, you'll need to replace your sender_username & receiver_username with 4 columns:

sendable_id
sendable_type

receiveable_id
receiveable_type

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