如何在Rails中刪除使用collection_select保存的記錄？

Question

我的目標是能夠在從一個collection_select中取消選擇項目時更新已保存的記錄（然後重新提交該記錄。）在此先感謝您的幫助！

詳細

我已經有了一個Newsavedmaps一種形式。 Newsavedmaps可以有很多路標。用戶可以在collection_select中選擇航點，並且當他們保存Newsavedmap時，這些航點將保存到他們自己的數據庫表中。

問題：當用戶打開他們保存的Newsavedmap時，我希望他們能夠取消選擇一個航點。當他們再次保存Newsavedmap時，我想要刪除選定的航點。

這是我維護的Rails 2.3X應用程序，這就是爲什麼collection_select使用下面的不同格式。

型號

class Newsavedmap < ActiveRecord::Base 
    belongs_to :itinerary 
    has_many :waypoints, :dependent => :destroy 
    accepts_nested_attributes_for :waypoints, :reject_if => lambda { |a| a[:waypointaddress].blank? }, :allow_destroy => true 
end 

查看

<% form_for @newsavedmap, :html => { :id => 'createaMap' } do |f| %> 
     <%= f.error_messages %>    
     <%= f.text_field :name, {:id=>"savemap_name", :size=>30 }%></p> 

     <%= collection_select :waypoints, :waypointaddress, @newsavedmap.waypoints, :waypointaddress, :waypointaddress, {}, { :multiple => true, :class => "mobile-waypoints-remove", :id =>"waypoints" } %> 

    <% end %> 

Newsavedmaps控制器

def create 
    @newsavedmap = Newsavedmap.new(params[:newsavedmap]) 
    waypoint = @newsavedmap.waypoints.build 

    respond_to do |format| 
    if @newsavedmap.save 
     flash[:notice] = 'The new map was successfully created.' 
     format.html { redirect_to "MYURL"} 
     format.xml { render :xml => @newsavedmap, :status => :created, :location => @newsavedmap } 
    else 
     format.html { render :action => "new" } 
     format.xml { render :xml => @newsavedmap.errors, :status => :unprocessable_entity } 
    end 
    end 
end 


def update 
    @newsavedmap = Newsavedmap.find(params[:id]) 

    if @newsavedmap.itinerary.user_id == current_user.id 
    respond_to do |format| 
     if @newsavedmap.update_attributes(params[:newsavedmap]) 
     flash[:notice] = 'Newsavedmap was successfully updated.' 
     format.html { redirect_to "MYURL" } 
     format.xml { head :ok } 
     else 
     format.html { render :action => "edit" } 
     format.xml { render :xml => @newsavedmap.errors, :status => :unprocessable_entity } 
     end 
    end 
    else 
    redirect_to '/' 
    end 
end 

創建新記錄時的參數

參數：{「newsavedmap」=> {「name」=>「我的地圖名稱」，其他字段不在上面，「waypoints」=> {「waypointaddress」=> 「1600賓夕法尼亞大道西北，華盛頓特區20500」，「350 5th Ave，紐約，紐約10118」]}}

Answer 1

我認爲你的問題是正確建立的形式（和它來自它的參數）。

我建議

1. 看看寶石cocoon或nested_form
2. 添加waypoints_attributes到attr_accessible
3. 在窗體

和Rails實現傭工從寶石（從點＃1）魔術應該做其他工作

Answer 2

另一個變種（不使用寶石）（我覺得難多了！）

你可以刪除accept_nested_attributes，並直接使用你的params。但在這種情況下，您應該手動管理所有進程：正確插入記錄，正確銷燬它們。

在你的情況下，它應該像這樣（沒有測試！）。該示例基於您在問題中發佈的參數。

def create 
    # delete params 'waypoints' it will be manage manually 
    waypoints = params[:newsavedmap].delete(:waypoints) 
    @newsavedmap = Newsavedmap.new(params[:newsavedmap]) 
    waypoints.each do |waypoint| 
    @newsavedmap.waypoints.build(:waypointaddress => waypoint) 
    end 
    if @newsavedmap.save 
    ... 
    end 
end 

主要的麻煩將在方法update

def update 
    # delete params 'waypoints' it will be manage manually 
    waypoints = params[:newsavedmap].delete(:waypoints) 

    # find and setup attributes 
    @newsavedmap = Newsavedmap.find(params[:id]) 
    @newsavedmap.attributes = params[:newsavedmap] 

    # TROUBLES start here 
    # destroy not checked (but existed in DB) waypoints 
    existed_waypoints = @newsavedmap.waypoints 
    existed_waypoint_addresses = existed_waypoints.map(&:waypointaddress) 
    new_waypoints = [] 
    waypoints.each do |waypoint| 
    if existed_waypoint_addresses.include?(waypoint) 
     # existed waypoint was selected on the form 
     # find it and add to new_waypoints 
     new_waypoints << @newsavedmap.waypoints.find_by_waypointaddress(waypoint) 
    else 
     # new waypoint was selected on the form 
     # build it and add to new_waypoints 
     new_waypoints << @newsavedmap.waypoints.build(:waypointaddress => waypoint) 
    end 
    end 
    # setup new records for waypoints 
    @newsavedmap.waypoints = new_waypoints 

    if @newsavedmap.save 
    # destroy existed but not selected waypoints 
    (existed_waypoints - new_waypoints).map(&:destroy) 
    ... 
    end 
end