Ruby on Rails creating multiple children in one parent form - ruby-on-rails

Question

I have a parent which has multiple children. I want it so that when I submit my form, a parent is generated in the parent model, and multiple records are created in the child model, one for each child. When I try and submit, I get the following error:
ActiveRecord::AssociationTypeMismatch in ParentsController#create
Child(#) expected, got Array(#)
When I uncomment accepts_nested_attributes_for :children and change f.fields_for :children to f.fields_for :children_attributes, I get a different error:
TypeError in ParentsController#create
can't convert Symbol into Integer
I am at a loss as to what to do. I have checked out the nested model forms railscasts, but they were dealing with generating children fields inside the form, and what I learned from the railscasts didn't seem to work. I am pretty I am doing my builder.text_field :cname's in my form wrong, but I'm not aware of the proper way to do it.
My code:
parent.rb
class Parent < ActiveRecord::Base
has_many :children
#accepts_nested_attributes_for :children
attr_protected :id
child.rb
class Child < ActiveRecord::Base
belongs_to :parent
attr_protected :id
_form.html.erb
<%= form_for #parent, :url => { :action => "create" } do |f| %>
<%= f.text_field :pname %>
<%= f.fields_for :children do |builder| %>
<%= builder.text_field :cname %>
<%= builder.text_field :cname %>
<%= builder.text_field :cname %>
<% end %>
<%= f.submit %>
<% end %>
params content:
{"utf8"=>"✓",
"authenticity_token"=>"FQQ1KdNnxLXolfes9IGiO+aKHJaPCH+2ltDdA0TwF7w=",
"parent"=>{"pname"=>"Heman",
"child"=>{"cname"=>""}},
"commit"=>"Create"}

Answer 1

The problem here is that the generated form in HTML for the children are using the same "place" (same pair key/value) in the params Hash (using the params[:parent][:child][:cname] pair). This is why there is only one param 'name' in the 'child' node in the Params hash.
To avoid that, you can use an array for the input's name:
<input type="text" name="child[][cname]" />
<input type="text" name="child[][cname]" />
The params, when this submitted, will look like this:
params: {
child: [ { cname: 'blabla' }, { cname: 'bonjour' } ]
}
To get the desired result, in your case:
<%= form_for #parent, :url => { :action => "create" } do |f| %>
<%= f.text_field :pname %>
<%= text_field_tag "parent[children][][cname]" %>
<%= text_field_tag "parent[children][][cname]" %>
<%= text_field_tag "parent[children][][cname]" %>
<%= f.submit %>
<% end %>
Should produce something like this:
{
"utf8"=>"✓",
"authenticity_token"=>"FQQ1KdNnxLXolfes9IGiO+aKHJaPCH+2ltDdA0TwF7w=",
"parent"=> {
"pname"=>"Heman",
"children"=> [
{ "cname"=>"SisiSenior" },
{ "cname"=>"Bonjor" },
{ "cname"=>"Blabla" }
]
},
"commit"=>"Create"}
So in your controller, you could use something like this:
#ParentsController
def create
children_attributes = params[:parent].delete(:children) # takes off the attributes of the children
#parent = Parent.create(params[:parent])
children_attributes.each do |child_attributes|
child = #parent.children.create(child_attributes)
end
end