ruby on rails - How do I add a data association between records in a HABTM many to many relationship? -

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i have set habtm relationship between 2 table creating many many relationship between items , categories. want add item connected 1 or more categories via add item form. when submit form getting error "can't mass-assign protected attributes: categories".

here models:

class item < activerecord::base   attr_accessible :description, :image, :name    has_attached_file :image, :styles => { :medium => "300x300>", :thumb => "100x100>" }    belongs_to :user   has_and_belongs_to_many :categories    validates :name, presence: true, length: {maximum: 50}   accepts_nested_attributes_for :categories end  class category < activerecord::base   attr_accessible :description, :name   has_and_belongs_to_many :items    validates :name, presence: true, length: {maximum: 50} end

and migrations:

class createitems < activerecord::migration   def change     create_table :items |t|       t.string :name       t.text :description       t.has_attached_file :image        t.timestamps     end   end end  class createcategories < activerecord::migration   def change     create_table :categories |t|       t.string :name       t.string :description        t.timestamps     end   end end  class createcategoriesitems < activerecord::migration   def     create_table :categories_items, :id => false |t|       t.integer :category_id       t.integer :item_id     end   end    def down     drop_table :categories_items   end end

and form looks this:

<%= form_for(@item, :html => { :multipart => true }) |f| %>   <%= render 'shared/error_messages', object: f.object %>     <%= f.label :name %>   <%= f.text_field :name %>    <%= f.label :description %>   <%= f.text_field :description %>   <%= f.file_field :image %>   <%= f.collection_select(:categories, @categories,:id,:name)%>   <%= f.submit "add item", :class => "btn btn-large btn-primary" %> <% end %>

and here's items controller:

class itemscontroller < applicationcontroller    def new     @item = item.new     @categories = category.all   end    def create     @item = item.new(params[:item])     if @item.save       #sign_in @user       flash[:success] = "you've created item!"       redirect_to root_path     else       render 'new'     end   end    def show   end    def index     @items = item.paginate(page: params[:page], per_page: 3)   end   end

thanks of :)

-rebekah

mass assignment means passing attributes call creates object part of attributes hash.

try this:

@item = item.new(name: 'item1', description: 'description1') @item.save @category = category.find_by_name('category1') @item.categories << @category

also see:

http://guides.rubyonrails.org/association_basics.html#the-has_and_belongs_to_many-association http://api.rubyonrails.org/classes/activemodel/massassignmentsecurity/classmethods.html

i hope helps.


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