Create a post with many-to-many relationship in Ruby on Rails - ruby-on-rails

Question

I have a structure very much for between category and yell. What I do is qeuro a call on POST type API with the following parameters:
{
"user_id":"1",
"title":"primeito",
"desciption":"de_novo",
"categories":[{"name":"eletro"},{"name":"domestic"},{"name":"new_category"}],
"yell_type":"novo",
"price":"10,00",
"payment_type":"boleto"
}
My structure is as follows:
My model yell:
#yell.rb
class Yell < ActiveRecord::Base
belongs_to :user, inverse_of: :yells
has_and_belongs_to_many :categories
end
model category:
#category.rb
class Category < ActiveRecord::Base
has_and_belongs_to_many :yells
end
method crete in controller yell:
#yells_controller.rb
def create
#yell = Yell.new(yell_params)
params[:categories].each do |rel|
#category = Category.find_by_name(rel[:name])
if #category
#only creates the relationship
else
#yell.categories.build(name: rel[:name]) #creates the relationship and category
end
end
if #yell.save
render json: #yell, status: :created, location: api_yell_path(#yell)
else
render json: #yell.errors, status: :unprocessable_entity
end
end
...
private:
def yell_params
params.require(:yell).permit(:title, :desciption, :price, :payment_type, :user_id, :yell_type, :categories)
end
So I created the table
class CreateCategoriesYellsJoinTable < ActiveRecord::Migration
def self.up
create_table :categories_yells, :id => false do |t|
t.integer :category_id
t.integer :yell_id
end
add_index :categories_yells, [:category_id, :yell_id]
end
def self.down
drop_table :categories_yells
end
end
I can make him create the categories, but does not know how to create only the relationship. Agluem can help me is the comment #only creates the relationship?
I need to do this check because the category name is unique
Also if someone know something more elegant way to do this, I accept suggestions

Answer 1

I am not quite sure I understood the last paragraph, but I think you need an intermediate table to join the two models first.
You would need to create a table like this:
class CreateCategoriesAndYells < ActiveRecord::Migration
def change
create_table :categories_yells, id: false do |t|
t.belongs_to :category, index: true
t.belongs_to :yell, index: true
end
end
end
Then you would need to update your controller to say something like this:
#yell.categories.build(category_params)
You would need also to pass the category parameters to the controller.

Answer 2

In order to do so I had to create a model to join my table:
model category_yell.rb
class CategoriesYell < ActiveRecord::Base
belongs_to :category
belongs_to :yell
end
and create my method was as follows:
def create
##yell = Yell.new(yell_params.except(:categories))
#yell = Yell.new({title: params[:title], desciption: params[:desciption], price: params[:price], user_id: params[:user_id], yell_type: params[:yell_type]})
if #yell.save
Array(params[:categories]).each do |rel|
#category = Category.find_by_name(rel[:name])
if #category
#categories_yells = CategoriesYell.new(category_id: #category.id, yell_id: #yell.id)
if #categories_yells.save
#yell.categories.build(id: #category.id, name: rel[:name])#only creates the relationship
else
render json: {status: 1, message:"relationship categoy not create", data: #yell.errors}, status: :unprocessable_entity
end
else
#yell.categories.create(name: rel[:name]) #creates the relationship and category
end
end
render json: {status: 0, message:"sucess", data: #yell}, status: :created
else
render json: {status: -1, message:"error", data: #yell.errors}, status: :unprocessable_entity
end
end