Ruby on rails Rails有很多：通过关联。是否删除与链接的关联？

我有一个事件模型和一个用户模型，它们通过一个与会者模型连接在一起。我已经了解了如何以身份验证用户的身份“参加”活动。但我想不出一个“退出”活动的好方法。我确信这是我遗漏的一些琐碎的事情，但是有什么比问一些琐碎的事情更好的进入StackOverflow的方法呢？哦，我一直在搜索铁路乘客，所以几个小时

谢谢

views/events/show.html.erb

<p><strong>Attendees: </strong>
    <ul>
        <% for attendee in @event.users %>
            <% if attendee.username == current_user.username %>
                <li><strong><%= attendee.username %></strong>
                    <%= link_to 'Withdraw From Event', withdraw_event_path(@event.id), :method => :post, :class => 'btn btn-danger' %>
                    <%= link_to 'Destroy', @attendee, confirm: 'Are you sure?', method: :delete, :class => 'btn btn-danger' %>
                </li>
            <% else %>
                <li><%= attendee.username %></li>
            <% end %>
        <% end %>   
    </ul>
</p>

  def attend
    @event = Event.find(params[:id])
    current_user.events << @event
    redirect_to @event, notice: 'You have promised to attend this event.'
  end

  def withdraw
    # I can't get this to work
    redirect_to @event, notice: 'You are no longer attending this event.'
  end

class Event < ActiveRecord::Base
    attr_accessible :name, :location
    belongs_to :users

    has_many :attendees, :dependent => :destroy
    has_many :users, :through => :attendees

class User < ActiveRecord::Base
    has_many :events

    has_many :attendees, :dependent => :destroy
    has_many :events, :through => :attendees

class Attendee < ActiveRecord::Base
    belongs_to :event
    belongs_to :user

    attr_accessible :user_id, :event_id

    # Make sure that one user cannot join the same event more than once at a time.
    validates :event_id, :uniqueness => { :scope => :user_id }

end

与会者：


：post，：class=>“btn btn危险”%>
“btn btn危险”%>

/controllers/events\u controller.rb

<p><strong>Attendees: </strong>
    <ul>
        <% for attendee in @event.users %>
            <% if attendee.username == current_user.username %>
                <li><strong><%= attendee.username %></strong>
                    <%= link_to 'Withdraw From Event', withdraw_event_path(@event.id), :method => :post, :class => 'btn btn-danger' %>
                    <%= link_to 'Destroy', @attendee, confirm: 'Are you sure?', method: :delete, :class => 'btn btn-danger' %>
                </li>
            <% else %>
                <li><%= attendee.username %></li>
            <% end %>
        <% end %>   
    </ul>
</p>

  def attend
    @event = Event.find(params[:id])
    current_user.events << @event
    redirect_to @event, notice: 'You have promised to attend this event.'
  end

  def withdraw
    # I can't get this to work
    redirect_to @event, notice: 'You are no longer attending this event.'
  end

class Event < ActiveRecord::Base
    attr_accessible :name, :location
    belongs_to :users

    has_many :attendees, :dependent => :destroy
    has_many :users, :through => :attendees

class User < ActiveRecord::Base
    has_many :events

    has_many :attendees, :dependent => :destroy
    has_many :events, :through => :attendees

class Attendee < ActiveRecord::Base
    belongs_to :event
    belongs_to :user

    attr_accessible :user_id, :event_id

    # Make sure that one user cannot join the same event more than once at a time.
    validates :event_id, :uniqueness => { :scope => :user_id }

end

def出席
@event=event.find（参数[：id]）
current_user.events我想你找不到与会者了

def withdraw
  event    = Event.find(params[:id])
  attendee = Attendee.find_by_user_id_and_event_id(current_user.id, event.id)

  if attendee.blank?
    # handle case where there is no matching Attendee record
  end

  attendee.delete

  redirect_to event, notice: 'You are no longer attending this event.'
end

就这样！我知道这很琐碎。我忘了你可以写一个这样的方法，Rails还是Active Record？我会把它拼起来的。我希望其他人会发现这个简单的修复很有用。我有非常相似的代码，但我找不到retrach\u event\u路径（@event.id）-关于修复这个未定义方法的任何想法没有更好的方法吗？Attendee.find_by_user_id_和_event_id（当前_user.id，event.id）看起来很难看：/@FlorianWidtmann是的，很难看。：-）Rails 4中也不推荐使用它。您可以使用
Attendee.find\u by（用户标识：current\u user.id，事件标识：event.id）