Question

我试图在rails应用程序中实现基本信使系统。我正在关注一位在create方法中提出以下代码的指南。

    if Conversation.between?(params[:sender_id], params[:recipient_id]).present?
        @conversation = Conversation.between?(params[:sender_id],params[:recipient_id]).first
    else
        @conversation = Conversation.create!(conversation_params)
    end
    redirect_to conversation_messages_path(@conversation)
    end

目标是仅在没有为同一两个用户打开时创建新会话，否则会创建一个新会话。

我尝试使用此代码，但它返回错误：

undefined method `between?' for nil:NilClass

尽管@conversations不是零。方法之间？似乎没有。

我试图在

下面编写一个错综复杂的ActiveRecod查询

    @session = Conversation.where('recipient_id = params[:sender_id] and sender_id = params[:recipient_id]') + Conversation.where('recipient_id = params[:recipient_id] and sender_id = params[:sender_id]')

但它提出了

PG::UndefinedColumn: ERROR: column "params" does not exist LINE 1: ...ons".* FROM "conversations" WHERE (recipient_id = params[:se... ^ : SELECT "conversations".* FROM "conversations" WHERE (recipient_id = params[:sender_id] and sender_id = params[:recipient_id]) LIMIT $1

我的整个控制器如下：

class ConversationsController < ApplicationController

def index
    @users = User.all
    @profiles = Profile.all
    @conversations = Conversation.all
 end

def create

    @session = Conversation.where('recipient_id = params[:sender_id] and sender_id = params[:recipient_id]') + Conversation.where('recipient_id = params[:recipient_id] and sender_id = params[:sender_id]')

    if @session.present?
      @conversation = @session.first
    else
      @conversation = Conversation.create!(conversation_params)
    end
      redirect_to conversation_messages_path(@conversation)
end

private

def conversation_params
    params.permit(:sender_id, :recipient_id)
end
end

和我的对话模型

class Conversation < ApplicationRecord

  belongs_to :sender, :foreign_key => :sender_id, class_name: 'Profile'
  belongs_to :recipient, :foreign_key => :recipient_id, class_name: 'Profile'
  has_many :messages, dependent: :destroy
  validates_uniqueness_of :sender_id, :scope => :recipient_id

  scope :between, -> (sender_id,recipient_id) do
  where("(conversations.sender_id = ? AND conversations.recipient_id = ? ) OR (conversations.sender_id = ? AND conversations.recipient_id = ? )", sender_id,recipient_id, recipient_id, sender_id)
  end

end

最后我的观点

    <h1>conversations</h1>

<div class=”ui segment”>
    <h3>Mailbox</h3>
    <div class=”ui list”>
        <div class=”item”>
            <% @conversations.each do |conversation| %>
                <% if conversation.sender_id == current_user.id || conversation.recipient_id == current_user.id %>
                    <% if conversation.sender_id == current_user.id %>
                    <% recipient = User.find(conversation.recipient_id) %>
                <% else %>
                    <% recipient = User.find(conversation.sender_id) %>
                <% end %>
            <%= link_to recipient.firstname,   conversation_messages_path(conversation)%>
            <% end %>
            <% end %>
        </div>
    </div>
</div>

<div class=”ui segment”>
    <h3>All Users</h3>
    <div class=”ui list”>
        <% @users.each do |user| %>
        <% if user.id != current_user.id %>
        <div class=”item”>
            <%= user.firstname %>
            <%= link_to "Message me!", conversations_path(sender_id: current_user.id, recipient_id: user.id), method: :post %>
        </div>
        <% end %>
        <% end %>
    </div>
</div>

我希望有人可以就特定查询语法引发错误的原因发表评论。感谢

Answer 1

我会使用merge查询检查两个人之间是否有对话。

我猜您有sender和receiver这样的课程，例如User？

sender = User.find(first_user)
receiver = User.find(second_user)

if ((conversations = sender.conversations.merge(receiver.conversations)).any?)
  @conversation = conversations.first
else
  @conversation = Conversation.create(sender: sender, receiver: receiver)
end

Answer 2

我终于意识到Where查询的语法“attribute = value and attribute = value”与其他查询结合时会引发错误。不知道为什么。所以我转向传统的哈希语法“属性：值”，它起作用了。

使用rails中的逻辑运算符评估2个ActiveRecord .where查询

2 个答案: