How can I link to a nested child from outside the parent element in Rails 4?

问题

Ok, my situation. I have a nested resource of

    resources :projects do
        resources :campaigns
    end

I want to make a view with controller with

    resources :portfolios 

I want to make a <% link_to %> that listed all campaigns which I can do, but when I try to route the path i can't make it link to a campaign.

Example: in my portfolios/view/index.html.erb

<% @projects.each do |p| %>
  <% p.campaigns.each do |c| %>
    <div class="container" >
      <div>
        <%= link_to ( image_tag c.image_camp.url(:thumb)), p %>
      </div>
      <div class="col-md-2">
        <h3 style=""><%=link_to c.title, p %></h3>
        <h4><%= c.end_date %></h4>
        <h4><%= c.project_end %></h4>
      </div>
      <div class="col-md-6">
        <h4><%= c.project_end %></h4>
        <p><%= link_to "read more", p %></p>
      </div>
    </div>
  <% end %>
<% end %>

The above example links to the @project, I have tried putting 'c' in hopes it will link to the @campaign that I am obviously getting information from, but when I do I get the error

  undefined method `campaign_path' for #<#<Class:0x0000000cc74b68>:0x0000000ef964c0>

I've also tried project_campaigns_path(@project, campaign) and every other combination I could think of.

    undefined local variable or method `campaign' for #<#<Class:0x0000000cc74b68>:0x0000000ae94cd8>

I feel the problem lies in the portfolios_controller and that I have yet to understand how the controller affects routes and how to access those variables.

class PortfoliosController < ApplicationController
  def index
      @projects = Project.all.order('created_at DESC').includes(:campaigns)
  end
end

I assumed that @projects and @campaigns are both found as I am able to display everything on the portfolio/view, what am I missing?

回答1:

You need to pass the Project and the Campaign to the link_to. It will then know how to route to the nested resource.

来源：https://stackoverflow.com/questions/34096668/how-can-i-link-to-a-nested-child-from-outside-the-parent-element-in-rails-4