ArgumentError: wrong number of arguments (1 for 2)

Question

I'm very new to Rails, MVC, and CRUD, and I'm trying to use the update method to change the amount of votes on a post. I have the following code in my Posts Controller update method:

def update
    @post = Post.find(params[:id])

    if params[:vote] == 'up'
        @post.update_column(:ups => @post[:ups] + 1)
    elsif params[:vote] == 'down'
        @post.update_column(:downs => @post[:downs] + 1)
    end

    flash[:notice] = "Thanks for voting! This helps us determine important issues in our schools."

    redirect_to 'Posts#index'
end

and I have the following code in my routes.rb:

OpenMCJC::Application.routes.draw do
  root :to => 'posts#index'
  resources :posts
  match '/posts/:id/:vote', :to => 'posts#update'
end

After navigating to "/posts/3/up", it throws the following error:

ArgumentError in PostsController#update

wrong number of arguments (1 for 2)

The request parameters according to the page are as such:

{"id"=>"3",
"vote"=>"up"}

Can you help me figure out what went wrong?

Answer 1

update_column takes two arguments. You are only passing one.

Instead of:

@post.update_column(:ups => @post[:ups] + 1)

Try:

@post.update_column(:ups, @post[:ups] + 1)

This may seem like two arguments:

:ups => @post[:ups] + 1

but it's actually one hash.

With the more commonly used update_attributes, you can pass a hash:

@post.update_attributes(:ups => @post[:ups] + 1)

Answer 2

As Mischa pointed out, update_column takes two arguments. However, I would discourage you from using this method. First, it skips validations which may not be what you want. Second, Rails has built-in methods for incrementing or decrementing values. In your case, you could change your controller method to something like this:

if params[:vote] == 'up'
  @post.increment(:ups)
elsif params[:vote] == 'down'
  @post.increment(:downs)
end