Agile Web Development 4th ed. - Can't mass assign.error

rubyonrails-talk
1

I am new to Ruby and to Rails (using Ruby 1.9.3 and Rails 3.2.3) so I picked up the Agile Web Development book and have been working through it (apologies if this isn't the correct place for this question but the pragprog forums don't seem to work for me). I am currently working through the book and have reached the point where I am adding functionality to an "Add to Cart" button. Here is the code that was provided for the 'create' method in the line_item_controller:

def create

@cart = current_cart product = Product.find(params[:product_id]) @line_item = @cart.line_items.build(product: product)

...

end

This results in the following error when I click "Add to Cart"

Can't mass-assign protected attributes: product

Can anyone shed some light on what is going on here (my search-fu has failed me)? The only way that I have been able to get this to work is by changing the code (starting at @line_item) to:

@line_item = @cart.line_items.build @line_item.product = product

Is this correct or is it just a band-aid fix that may cause issues going forward?

Thanks,

2

Quoting Lucas J. <lists@ruby-forum.com>:

I am new to Ruby and to Rails (using Ruby 1.9.3 and Rails 3.2.3) so I picked up the Agile Web Development book and have been working through it (apologies if this isn't the correct place for this question but the pragprog forums don't seem to work for me). I am currently working through the book and have reached the point where I am adding functionality to an "Add to Cart" button. Here is the code that was provided for the 'create' method in the line_item_controller:

def create

@cart = current_cart product = Product.find(params[:product_id]) @line_item = @cart.line_items.build(product: product)

...

end

This results in the following error when I click "Add to Cart"

Can't mass-assign protected attributes: product

Can anyone shed some light on what is going on here (my search-fu has failed me)? The only way that I have been able to get this to work is by changing the code (starting at @line_item) to:

@line_item = @cart.line_items.build @line_item.product = product

Is this correct or is it just a band-aid fix that may cause issues going forward?

This is a correct way to do it now. And probably the best way to move forward with the tutorial right now. The newest releases of Rails have made mass-assign protection the default. Without it you have a security risk. You can learn more by Googling "Rails mass assign". Save it for after you complete the book.

HTH,   Jeffrey

3

what about use google a bit? there's about 2.460.000 resuls for "Can't mass-assign protected attributes:" query

set attr_accessible in your model(s)

tom

4

Thanks, Jeffrey. I just wanted to ensure that I was on the right track and that I wasn't setting myself up for more problems later.

Tom - I tried google first (I always do). My attributes are already set to attr_accessible in my models (there are only three at this point), which is why I was so confused. I'm sure there's something I'm overlooking but I'm not going to spend too much more time on it since I have a working solution at this point.

5

Thanks, Jeffrey. I just wanted to ensure that I was on the right track and that I wasn't setting myself up for more problems later.

Tom - I tried google first (I always do). My attributes are already set to attr_accessible in my models (there are only three at this point), which is why I was so confused. I'm sure there's something I'm overlooking but I'm not going to spend too much more time on it since I have a working solution at this point.

If you want to be able to do line_items.build(product: p) you need to mark product as attr_accessible too. The mass assignment stuff doesn't know what things are database attributes, virtual attributes, associations etc.

Fred

6

maybe you miss the code in the book:

file: line_item.rb

belong_to :product

belong_to :cart

then, the line_item has the attr product.