如何为收件箱消息传递设置上一条/下一条消息

Question

我创建了一个收件箱消息系统，它工作得很完美。但是，我不知道如何实现消息的上一个和下一个功能(因此用户可以在查看一个时转到下一个或上一个消息)。这些都是在互联网上查看信息的正常功能。Previous应该是指消息创建时间的Previous。如有任何帮助，不胜感激。

messages_controller:

  before_filter :set_user
  def index
    if params[:mailbox] == "sent"
      @messages = @user.sent_messages
    elsif params[:mailbox] == "inbox"
      @messages = @user.received_messages
    #elsif params[:mailbox] == "archieved"
     # @messages = @user.archived_messages
    end
    if params[:mailbox] == "unread"
    @messages = @user.unread_messages
  end
  end
  def new
    @message = Message.new
    if params[:reply_to]
      @reply_to = User.find_by_user_id(params[:reply_to])
      unless @reply_to.nil?
        @message.recipient_id = @reply_to.user_id
      end
    end
  end
  def create
    @message = Message.new(params[:message])
    @message.sender_id = @user.id
    if @message.save
      flash[:notice] = "Message has been sent"
      redirect_to user_messages_path(current_user, :mailbox=>:inbox)
    else
      render :action => :new
    end
  end
  def show
     @message = Message.find(params[:id])
     @message.readingmessage if @message.recipient == current_user
   end
   def destroy
     @message = Message.find(params[:id])
     @message.destroy
     flash[:notice] = "Successfully deleted message."
     redirect_to user_messages_path(@user, @messages)
   end
  def delete_multiple
      if params[:delete]
        params[:delete].each { |id|
          @message = Message.find(id)
          @message.mark_message_deleted(@message.id,@user.id) unless @message.nil?
        }
        flash[:notice] = "Messages deleted"
      end
      redirect_to user_messages_path(@user, @messages)
  end
  private
    def set_user
      @user = current_user
    end
end

消息模型:

attr_accessible :subject, :body, :sender_id, :recipient_id, :read_at,:sender_deleted,:recipient_deleted
    validates_presence_of :subject, :message => "Please enter message title"
    belongs_to :sender,
    :class_name => 'User',
    :foreign_key => 'sender_id'
    belongs_to :recipient,
    :class_name => 'User',
    :foreign_key => 'recipient_id'
    # marks a message as deleted by either the sender or the recipient, which ever the user that was passed is.
    # When both sender and recipient marks it deleted, it is destroyed.
    def mark_message_deleted(id,user_id)
         self.sender_deleted = true if self.sender_id == user_id
         self.recipient_deleted = true if self.recipient_id == user_id
         (self.sender_deleted && self.recipient_deleted) ? self.destroy : self.save!
     end
    # Read message and if it is read by recipient then mark it is read
    def readingmessage
      self.read_at ||= Time.now
      save
    end
    # Based on if a message has been read by it's recipient returns true or false.
    def read?
        self.read_at.nil? ? false : true
    end
    def self.received_by(user)
       where(:recipient_id => user.id)
     end
     def self.not_recipient_deleted
       where("recipient_deleted = ?", false)
     end
     def self.sent_by(user)
        Message.where(:sender_id => user.id)
      end
    end

show.html(消息视图):

    <strong>From:</strong> 
    <%= @message.sender %>
</p>
<p>
    <strong>Received:</strong> 
    <%= @message.created_at.to_s(:long) %>
</p>
<p>
    <strong>To:</strong> 
    <%= @message.recipient %>
</p>
<p>
    <strong>Message</strong><br />
    <%=h @message.body %>
</p>
<p>
    <% if @message.recipient == @user %>
    <%= link_to "Reply", new_user_message_path(@user, :reply_to => @message.sender) %>
     |
    <% end %>
    <%= link_to "Inbox", user_messages_path(current_user, :mailbox=>:inbox)%>
    |
    <%= link_to "Delete", [current_user, @message], :confirm => 'Are you sure you want to delete this message?', :method => :delete %>
</p>

Answer 1

在Message模型中:

def previous(same_recipient = true)
  collection = Message.where('id <> ? AND updated_at > ?', self.id, self.updated_at).order('updated_at ASC')
  collection.where(recipient_id: self.recipient_id) if same_recipient
  collection.first
end
def next(same_recipient = true)
  collection = Message.where('id <> ? AND updated_at < ?', self.id, self.updated_at).order('updated_at DESC')
  collection.where(recipient_id: self.recipient_id) if same_recipient
  collection.first
end

这是我们在日历系统中使用的，非常有用的上一步/下一步与约会。

这依赖于updated_at列，这有点糟糕(如果我更新旧消息，它会混淆下一个/上一个消息)。也许您想使用created_at列，或者您自己的列。你可以在视图中这样做:

# [...]
<p>
  <strong>Message</strong><br />
  <%=h @message.body %>
</p>
<p>
  <%= link_to 'Next', user_message_path(current_user, @message.next) %>
  <%= link_to 'Previous', user_message_path(current_user, @message.previous) %>
</p>

Answer 2

在用于查看消息的控制器中，从DB获取3条消息，并将中间条目显示为当前消息。将ID设置为上一条和下一条消息的变量。

然后在视图中创建两个按钮:previous和next，其中它们的链接url是您保存的id的路径。