如何在Rails中以嵌套形式更新子记录

Question

How would I update a collection of child 'Product' rows when submitting the form below.

Many thanks

class User < ActiveRecord::Base                                                                                                                                                                             
   has_many :products, :class_name => 'Product', :inverse_of => :user                                                                                                                                       
   accepts_nested_attributes_for :products                                                                                                                                                                  
end                                                                                                                                                                                                         

class Product < ActiveRecord::Base                                                                                                                                                                          
    belongs_to :user, :inverse_of => :products                                                                                                                                                          
end   

The View

<%= form_for(@user) do |f| %>                                                                                                                                                                               

  <div class="field">                                                                                                                                                                                       
    <%= f.label :name %><br>                                                                                                                                                                                
    <%= f.text_field :name %>                                                                                                                                                                               
  </div>                                                                                                                                                                                                    
  <%= f.fields_for :products do |builder| %>                                                                                                                                                                
      <% builder.text_field :name %>                                                                                                                                                                    
  <% end %>                                                                                                                                                                                                 
  <div class="actions">                                                                                                                                                                                     
    <%= f.submit %>                                                                                                                                                                                         
  </div>                                                                                                                                                                                                    
<% end %>                                                                                                                                                                                                   

Answer 1

Here is somewhat minimal update action:

# app/controller/users_controller.rb

def update 
  # Get the user in param
  @user = User.find(params[:id])

  # Update attributes
  if @user.update_attribute(params[:user]) 
    # Redirect to :show for this user.  
    redirect_to :show
  else 
    # update_attriubtes failed.  Render the edit view. 
    render :edit
  end
end

Secondly, you also need to ensure the attributes can be mass assigned such that the call to @user.update_attributes succeeds. Since you've not tagged your question with the appropriate Rails version, following is what you can do for Rails 3 and Rails 4:

1. Rails 3 - Define each attribute you want to mass assign as attr_accessible
2. Rails 4 - Permit parameters in controllers params.require(:user).permit(...) .

Note that in your view you are not outputting the result of the helper text_field on this line:

<% builder.text_field :name %> 

You need to use <%=...%> (note the equals = sign) in order to output the result of expressions within <%=...%> . This might have just been a typo here as you've done this correctly on all other elements. Replace the line with:

<%= builder.text_field :name %>

Also, suggest reading the " Action Controller Overview " of guides for details on Controllers.