Rails索引方法显示带有子记录的父级

Question

know this is a bone-headed question, but I cant find what im looking for.

I have two models: parent and child

class child < ActiveRecord::Base
  belongs_to :parent
end

class parent < ActiveRecord::Base
  has_many :childs
end

in the child controller index action I would like to display a field from the parent model with each of the queried records.

def index
  @childs = Childs.all
end

How do I display the parent_name in the view with the child records?

for example:

<%= @childs.each do |c| %>
  <%= child.name %>
  <%= child.parent.name %>
<% end %>

Answer 1

Here is a list of issues that I found with your code.

• Your model names should be capitalized.
• When setting the association, your childs should be children .
• When setting @childs , your should reference the model as Child , not Childs
• You're looping through each record of the children with c but you reference them as child
• There is no need for <%= in the first line.

Correcting these should look like this and it should work. If you are having other issues, post the error message and relevant code.

Models

class Child < ActiveRecord::Base
  belongs_to :parent
end

class Parent < ActiveRecord::Base
  has_many :children
end

Controller

def index
  @childs = Child.all
end

View

<% @childs.each do |child| %>
  <%= child.name %>
  <%= child.parent.name %>
<% end %>

Answer 2

If you're having a nil class, maybe it's because your :parent_id doesn't carry your parent's id when creating the record.

You may go to rails console and enter 'Child.all' to see if all your :parent_ids are nil or not.

I myself have a user model that has_many :tweets，and each tweet model belongs_to :user. In my tweet.controller.rb, I set up the def create as follows to enter user's id into :user_id column:

def create
    @tweet = current_user.tweets.new(tweet_params)
    if @tweet.save
      flash[:notice] = "You've updated with a tweet."
      redirect_to admin_tweets_path
    else
      @tweets = Tweet.all
      render :index
    end
  end