Question

我该如何解决这个问题？

我有2个按钮： /views/subjects/_inscription_button.html.haml

  - if subject.participation(current_participant).nil?
    = link_to "Ca m'intéresse !",   subject_participant_index_path(:interested_id => current_participant.id, :subject_id => subject.id), remote: true, :method => :post, class:"btn btn-primary"

  - else
    = link_to "Ca ne m'intéresse plus !",   delete_participation_path(@subject.participation(current_participant).id),:method => :delete, remote: true, class:"btn btn-primary"

第二个link_to并不想正常切换。我收到错误：

/ subject_participant / 115的NoMethodError 未定义的方法`id＆＃39;为零：NilClass

实例变量subject适用于第一个按钮但不适用于第二个按钮...

以下是其他有用的代码： subject_participant_controller.rb：

class SubjectParticipantController < ApplicationController
  before_action :authenticate_participant!


  def create
   @subject = Subject.find(params[:subject_id])
   @subject_participant = SubjectParticipant.new(subject_participant_params)

   if @subject_participant.save
     respond_to do | format |
      format.html {redirect_to subjects_path}
      format.js
     end
   else
    redirect_to subjects_path
   end
  end

  def destroy
    @subject_participant = SubjectParticipant.find(params[:id])
    if @subject_participant.destroy
     respond_to do | format |
      format.html {redirect_to subjects_path}
      format.js
     end
    else
     redirect_to subjects_path
    end
  end

  def subject_participant_params
    params.permit(:interested_id, :subject_id, :id)
  end
end

/routes.rb：

Rails.application.routes.draw do
 devise_for :participants
 resources :subjects
 resources :participants
 resources :conferences
 resources :subject_participant

 delete 'subject_participant/:id' => 'subject_participant#destroy', as: 'delete_participation'
 root 'welcome#index'

subject.rb中

class Subject < ActiveRecord::Base
  validates_presence_of  :title, :questioner, :conference, :description

  has_many :subject_participants
  has_many :interested, through: :subject_participants #interested
  belongs_to :questioner, class_name: "Participant"
  belongs_to :conference

  def participation(current_participant) 
   self.subject_participants.find_by_interested_id(current_participant.id)
 end
end

Answer 1

它告诉你@subject.participation(current_participant)是零。你需要解决它。

请记住，在Rails视图中使用实例变量时，需要在相应的控制器操作中定义它们。从您的部分向后退到其父视图。它与哪种控制器动作有关？

您可以在此处定义部分所需的实例变量。

Answer 2

只需用户@subject代替主题。

- if subject.participation(current_participant).nil?
= link_to "Ca m'intéresse !",subject_participant_index_path(:interested_id => current_participant.id, :subject_id => @subject.id), remote: true, :method => :post, class:"btn btn-primary"

- else
= link_to "Ca ne m'intéresse plus !",   delete_participation_path(@subject.participation(current_participant).id),:method => :delete, remote: true, class:"btn btn-primary"

我怎样才能在link_to中使用实例变量？

2 个答案: