DataMapper Associations 'NoMethodError‘

Question

我被一个问题困住了，不知道问题出在哪里。因为我是相对较新的，所以你可以希望帮助我:)。

首先，我使用padrino和datamapper gem。

我有一个带one_to_many关系的旅行和住宿模式

模型的样子：Trip.rb

class Trip
  include DataMapper::Resource

  # Associations
  has n, :accommodations

  property :id, Serial, :key => true
  # many more properties
end

Accommodation.rb

class Accommodation
  include DataMapper::Resource

  has n, :appartments
  belongs_to :trip, :child_key => [:trip_id]

  # property <name>, <type>
  property :id, Serial
end

根据dm文档，我假设关联是有效的。

我想达到以下的申请行为：

用户可以选择一次特定的旅行，并添加或删除住宿。

这就是我的控制器的样子：trips.rb

HhtBackoffice.controllers :trips do
  get :index do
    @trips = Trip.all
    render 'trips/index'
  end

  get :show, :with => :id do
    @trip = Trip.get(params[:id])
    set_current_trip(Trip.get(params[:id]))
    render 'trips/show'
  end

  get :new do
    @trip = Trip.new
    render 'trips/new'
  end

  post :create do
    @trip = Trip.new(params[:trip])
    if @trip.save
      flash[:notice] = 'Neue Reise wurde erfolgreich hinzugefügt'
      redirect url(:trips, :edit, :id => @trip.id)
    else 
      render 'trips/new'
    end
  end
..........
more code
........
end

accommodations.rb

HhtBackoffice.controllers :accommodations do
  get :index do
    @accommodations = Accommodation.all
    render 'accommodations/index'
  end

  get :new do
    @trip = current_trip
    @accommodation = @trip.accommodations.new  # <-- This function is not known according to the error
    render 'accommodations/new'
  end

  post :create do
    @trip = current_trip
    @accommodation = @trip.accommodations.new(params[:accommodation])
    if @accommodation.save
      flash[:notice] = 'Neue Reise wurde erfolgreich hinzugef&uuml;gt'
      redirect url(:accommodations, :edit, :id => @accommodation.id)
    else 
      render 'accommodations/new'
    end
  end
.... more code here ....
end

如您所见，我使用了两个助手函数。set_current_trip (调用显示视图时)以跟踪当前行程。和current_trip去拿current_trip。

这是我的trips/show.haml视图

.block
    .secondary-navigation
        %ul.wat-cf
            %li.first.active=link_to pat(:list), url(:trips, :index)
            %li=link_to pat(:new), url(:trips, :new)
    .content
        %h2.title
            
        .inner
            -@trip.accommodations.each do |acco|
                %ud
                    %li= acco.id
                    %li= acco.name
            =button_to pat(:new), url(:accommodations, :new), :method => :get, :class => :button_to

        .actions-bar.wat-cf
            .actions=" "

这是accommodations/new视图

.block
  .secondary-navigation
    %ul.wat-cf
      %li.first=link_to pat(:list), url(:accommodations, :index)
      %li.active=link_to pat(:new), url(:accommodations, :new)
  .content
    %h2.title
      =pat(:new)
      =mt(:accommodation)
    .inner
      -form_for :accommodation, url(:accommodations, :create), :class => :form do |f|
        =partial "accommodations/form", :locals => { :f => f }

这是错误

#<NoMethodError: undefined method `accommodations' for nil:NilClass>

/home/paddy/Projects/hht_backoffice/app/controllers/accommodations.rb in block (2 levels) in <top (required)>
    @trip.accommodations.new
/home/paddy/.rvm/gems/ruby-1.9.3-p374/gems/padrino-core-0.10.7/lib/padrino-core/application/routing.rb in call
            proc { |a,p| unbound_method.bind(a).call }
/home/paddy/.rvm/gems/ruby-1.9.3-p374/gems/padrino-core-0.10.7/lib/padrino-core/application/routing.rb in block in route
            proc { |a,p| unbound_method.bind(a).call }
/home/paddy/.rvm/gems/ruby-1.9.3-p374/gems/padrino-core-0.10.7/lib/padrino-core/application/routing.rb in []
        halt_response     = catch(:halt) { route_eval { @route.dest[self, @block_params] } }
/home/paddy/.rvm/gems/ruby-1.9.3-p374/gems/padrino-core-0.10.7/lib/padrino-core/application/routing.rb in block (3 levels) in process_destination_path
        halt_response     = catch(:halt) { route_eval { @route.dest[self, @block_params] } }
/home/paddy/.rvm/gems/ruby-1.9.3-p374/gems/sinatra-1.3.4/lib/sinatra/base.rb in route_eval
      throw :halt, yield
/home/paddy/.rvm/gems/ruby-1.9.3-p374/gems/padrino-core-0.10.7/lib/padrino-core/application/routing.rb in block (2 levels) in process_destination_path
        halt_response     = catch(:halt) { route_eval { @route.dest[self, @block_params] } }
/home/paddy/.rvm/gems/ruby-1.9.3-p374/gems/padrino-core-0.10.7/lib/padrino-core/application/routing.rb in catch
        halt_response     = catch(:halt) { route_eval { @route.dest[self, @block_params] } }
/home/paddy/.rvm/gems/ruby-1.9.3-p374/gems/padrino-core-0.10.7/lib/padrino-core/application/routing.rb in block in process_destination_path
        halt_response     = catch(:halt) { route_eval { @route.dest[self, @block_params] } }
/home/paddy/.rvm/gems/ruby-1.9.3-p374/gems/padrino-core-0.10.7/lib/padrino-core/application/routing.rb in instance_eval
    Thread.current['padrino.instance'].instance_eval do
/home/paddy/.rvm/gems/ruby-1.9.3-p374/gems/padrino-core-0.10.7/lib/padrino-core/application/routing.rb in process_destination_path
    Thread.current['padrino.instance'].instance_eval do
/home/paddy/.rvm/gems/ruby-1.9.3-p374/gems/http_router-0.10.2/lib/http_router/node/root.rb in []
      end
/home/paddy/.rvm/gems/ruby-1.9.3-p374/gems/http_router-0.10.2/lib/http_router.rb in block in call
    response = catch(:success) { @root[request] }
/home/paddy/.rvm/gems/ruby-1.9.3-p374/gems/http_router-0.10.2/lib/http_router.rb in catch
    response = catch(:success) { @root[request] }
/home/paddy/.rvm/gems/ruby-1.9.3-p374/gems/http_router-0.10.2/lib/http_router.rb in call
    response = catch(:success) { @root[request] }
/home/paddy/.rvm/gems/ruby-1.9.3-p374/gems/padrino-core-0.10.7/lib/padrino-core/application/routing.rb in route!
          if base.compiled_router and match = base.compiled_router.call(@request.env)
/home/paddy/.rvm/gems/ruby-1.9.3-p374/gems/padrino-core-0.10.7/lib/padrino-core/application/routing.rb in dispatch!
          route!
/home/paddy/.rvm/gems/ruby-1.9.3-p374/gems/sinatra-1.3.4/lib/sinatra/base.rb in block in call!
      invoke { dispatch! }
/home/paddy/.rvm/gems/ruby-1.9.3-p374/gems/sinatra-1.3.4/lib/sinatra/base.rb in block in invoke
      res = catch(:halt) { yield }
/home/paddy/.rvm/gems/ruby-1.9.3-p374/gems/sinatra-1.3.4/lib/sinatra/base.rb in catch
      res = catch(:halt) { yield }
/home/paddy/.rvm/gems/ruby-1.9.3-p374/gems/sinatra-1.3.4/lib/sinatra/base.rb in invoke
      res = catch(:halt) { yield }
/home/paddy/.rvm/gems/ruby-1.9.3-p374/gems/sinatra-1.3.4/lib/sinatra/base.rb in call!
      invoke { dispatch! }
/home/paddy/.rvm/gems/ruby-1.9.3-p374/gems/sinatra-1.3.4/lib/sinatra/base.rb in call
      dup.call!(env)
/home/paddy/.rvm/gems/ruby-1.9.3-p374/gems/sass-3.2.5/lib/sass/plugin/rack.rb in call
        @app.call(env)
/home/paddy/.rvm/gems/ruby-1.9.3-p374/gems/rack-1.5.1/lib/rack/head.rb in call
    status, headers, body = @app.call(env)
/home/paddy/.rvm/gems/ruby-1.9.3-p374/gems/rack-1.5.1/lib/rack/methodoverride.rb in call
      @app.call(env)
/home/paddy/.rvm/gems/ruby-1.9.3-p374/gems/padrino-core-0.10.7/lib/padrino-core/reloader.rb in call
        @app.call(env)
/home/paddy/.rvm/gems/ruby-1.9.3-p374/gems/padrino-core-0.10.7/lib/padrino-core/logger.rb in call
        status, header, body = @app.call(env)
/home/paddy/.rvm/gems/ruby-1.9.3-p374/gems/sinatra-1.3.4/lib/sinatra/showexceptions.rb in call
      @app.call(env)
/home/paddy/.rvm/gems/ruby-1.9.3-p374/gems/rack-1.5.1/lib/rack/session/abstract/id.rb in context
          status, headers, body = app.call(env)
/home/paddy/.rvm/gems/ruby-1.9.3-p374/gems/rack-1.5.1/lib/rack/session/abstract/id.rb in call
          context(env)
/home/paddy/.rvm/gems/ruby-1.9.3-p374/gems/sinatra-1.3.4/lib/sinatra/base.rb in block in call
        synchronize { prototype.call(env) }
/home/paddy/.rvm/gems/ruby-1.9.3-p374/gems/sinatra-1.3.4/lib/sinatra/base.rb in synchronize
          yield
/home/paddy/.rvm/gems/ruby-1.9.3-p374/gems/sinatra-1.3.4/lib/sinatra/base.rb in call
        synchronize { prototype.call(env) }
/home/paddy/.rvm/gems/ruby-1.9.3-p374/gems/padrino-core-0.10.7/lib/padrino-core/router.rb in block in call
        return app.call(
/home/paddy/.rvm/gems/ruby-1.9.3-p374/gems/padrino-core-0.10.7/lib/padrino-core/router.rb in each
      @mapping.each do |host, path, match, app|
/home/paddy/.rvm/gems/ruby-1.9.3-p374/gems/padrino-core-0.10.7/lib/padrino-core/router.rb in call
      @mapping.each do |host, path, match, app|
/home/paddy/.rvm/gems/ruby-1.9.3-p374/gems/rack-1.5.1/lib/rack/handler/webrick.rb in service
        status, headers, body = @app.call(env)
/home/paddy/.rvm/rubies/ruby-1.9.3-p374/lib/ruby/1.9.1/webrick/httpserver.rb in service
      si.service(req, res)
/home/paddy/.rvm/rubies/ruby-1.9.3-p374/lib/ruby/1.9.1/webrick/httpserver.rb in run
          server.service(req, res)
/home/paddy/.rvm/rubies/ruby-1.9.3-p374/lib/ruby/1.9.1/webrick/server.rb in block in start_thread

通过padrino控制台执行“相同”操作没有问题。

irb(main):001:0> @trip = Trip.get(1)
  DEBUG - (0.000101) SET sql_auto_is_null = 0
  DEBUG - (0.000127) SET SESSION sql_mode = 'ANSI,NO_BACKSLASH_ESCAPES,NO_DIR_IN_CREATE,NO_ENGINE_SUBSTITUTION,NO_UNSIGNED_SUBTRACTION,TRADITIONAL'
  DEBUG - (0.000092) SELECT `id`, `name`, `type`, `starts_at`, `ends_at`, `no_of_free_places`, `no_of_guests`, `raceday`, `created_at`, `updated_at` FROM `trips` WHERE `id` = 1 LIMIT 1
=> #<Trip @id=1 @name="Rofl" @type="Wettkampfreise" @starts_at=nil @ends_at=nil @no_of_free_places=nil @no_of_guests=nil @raceday=nil @created_at=#<DateTime: 2013-01-31T15:00:16+01:00 ((2456324j,50416s,0n),+3600s,2299161j)> @updated_at=#<DateTime: 2013-01-31T15:16:40+01:00 ((2456324j,51400s,0n),+3600s,2299161j)>>

irb(main):02:0> @trip.accommodations.new
=> #<Accommodation @id=nil @name=nil @no_of_appartments=nil @location=nil @capacity=nil @trip_id=1>

对解决这个问题有什么建议吗？

好吧，我猜到了。我的current_trip对象是零。这些是我的助手方法：

helper/trips.rb

  def set_current_trip(trip=nil)
    @current_trip = trip
  end

  def current_trip 
    @current_trip 
  end

提前谢谢！

编辑2

这是我的路线。也许嵌套是让它工作的好方法，我想打个电话

=button_to pat(:new), url(:accommodations, :new), :method => :get, :class => :button_to

在我的trips/show.haml里

但我明白错误

route mapping for url(:accommodations_new) could not be found!

为什么会这样呢？根据我的路线，我应该去/旅行/:trip_id/住宿/新的

路由

URL                           REQUEST  PATH
    (:accommodations, :index)        GET    /trips/:trip_id/accommodations
    (:accommodations, :new)          GET    /trips/:trip_id/accommodations/new
    (:accommodations, :create)      POST    /trips/:trip_id/accommodations/create
    (:accommodations, :edit)         GET    /trips/:trip_id/accommodations/edit/:id
    (:accommodations, :update)       PUT    /trips/:trip_id/accommodations/update/:id
    (:accommodations, :destroy)    DELETE   /trips/:trip_id/accommodations/destroy/:id
    (:base, :index)                 GET    /
    (:trips, :index)                GET    /trips
    (:trips, :show)                 GET    /trips/show/:id
    (:trips, :new)                  GET    /trips/new
    (:trips, :create)              POST    /trips/create
    (:trips, :edit)                 GET    /trips/edit/:id
    (:trips, :update)               PUT    /trips/update/:id
    (:trips, :destroy)            DELETE   /trips/destroy/:id

Answer 1

current_trip正在返回零。首先，在调用其中一个方法时，确保@trip不是零，因为如果尚未设置trip怎么办？

  get :new do
    @trip = current_trip
    if @trip
      @accommodation = @trip.accommodations.new  
      render 'accommodations/new'
    else
      # trip is nil. Call an error or something.
    end
  end

其次，我不确定您的助手方法是否会返回一个trip，因为@current_trip还没有初始化。current_trip是干什么用的？这是否是您希望用户跨会话持久存在的东西？如果是这样的话，您可能希望将current_trip保存在cookie中。

def set_current_trip(trip_id = 0)

  response.set_cookie 'current_trip', :value => trip_id, :path => '/', :expires => Time.now + 60 * 60 * 24 * 365 * 20

end

def current_trip 
  trip_id = request.cookies["current_trip"]
  current_trip = Trip.get trip_id
end