Rails：如何跨视图访问模型和控制器数据？

Question

I am creating an app to vote on your favorite lunch, and I'm reusing code that I learned from a tutorial (railstutorial.org.) I have a relatively simply hierarchy within my data models, which look like this:

Cuisine model:

has_many :providers
validates :name, presence: true, uniqueness: true

Cuisine has the following columns:

:id, :name

Provider model:

    belongs_to :cuisine
    has_many :lunches
    validates :name, presence: true, uniqueness: true
    validates :cuisine, presence: true

which has the following attributes:

:id, :name, :cuisine_id

Lunch model:

belongs_to :provider
default_scope -> { order('created_at DESC') }
validates :date, presence: true, uniqueness: true

Which has the following attributes:

:id, :date, :liked, :disliked, :provider_id, :lunchscore

A pretty straight forward inheritance model, to my untrained eye. What I am looking to do is list out all the different lunches that are associated with a provider, and highlight their score.

Provider Controller:

def show
    @provider = Provider.find(params[:id])
    @lunches = @provider.lunches
    @cuisine = @provider.cuisine

  end

In my Provider show.html.erb view , I have the following basic code:

<div class="title"><%= @provider.name.upcase %> </div> <div class="cuisine"> <%= @cuisine.name %>  </div>

<div class="span8">
    <% if @provider.lunches.any? %>
    <h3> Total Lunches - (<%= @provider.lunches.count %>) </h3>
    <%= render @lunches %>
    <% end %>
</div>

I also have a partial in the lunches folder called _lunch.html.erb which contains the following:

<ul>
    <span class="date_list"> <%= lunch.date %> - <%= @provider.name %>  </span>
        <span class="timestamp">Created <%= time_ago_in_words(lunch.created_at) %> ago. </span> 
  </span>
</ul>

This outputs the following to the page:

Total Lunches - (1) 2015-01-24 - Sophies Created 2 days ago.

Whilst this works (and that's great) I'm scratching my head trying to understand the behavior. Specifically:

1. Why put this partial in the lunches folder (as it is currently) instead of the provider folder? Does it have to be in the views/lunches folder?

2. Why is the render call written like an instance variable <%= render @lunches %> vs. specifying a folder, eg <%= render lunches/lunch %> ? Why doesn't the path need to be declared at all? how is rails transcribing @lunches into _lunch.html.erb?

3. Do I need to be rendering a partial in the lunches subfolder at all, or is there an easier way to access lunch data in a provider view?

Thanks in advance for likely a simple question. My app is working, I'm just trying to understand the behavior.

Answer 1

When you try to render an active record object by it self, rails converts that object into a partial by calling to_partial_path , which is by default the view/models/_model path, you can test it by calling something like Lunch.new.to_partial_path

if you try render a single lunch: render @lunch it would be equivalent to

render partial: 'lunches/lunch', locals: {lunch: @lunch}

I didn't know it supported using a collection render @lunches , but since you said it works so i guess it does, in this condition the equivalent would be something like

render partial: 'lunches/lunch', collection: @lunches, as: :lunch