Problems passing params when creating a model instance

Question

I have a Product.rb model in my Rails app, and it has a :title attribute and a :price attribute. From the Rails console I can successfully create an instance of one of these models, but I'm having trouble passing values for the :title and :price. Here's my products_controller:

class ProductsController < ApplicationController

def create

@product = Product.create(
  :name = params[:name],
  :price = params[:price]
  )
end

end

This is the command I use to create an instance:

Product.create("name", 123)

The :name attribute is set to be text and the :price attribute to be an integer. But when I hit enter this is what I got:

ArgumentError: wrong number of arguments (2 for 0..1)

I haven't written any Rails since before v4 and I'm a bit rusty. Anyone know the problem?

It should be :name => params[:name] etc, arrow, not assignment. — BroiSatse
– BroiSatse, Commented Jul 1, 2014 at 22:19

Jon · Accepted Answer · 2014-07-02 05:41:05Z

1

You're missing the > in your hash rockets.

Try this:

class ProductsController < ApplicationController

  def create
    @product = Product.create(
      :name => params[:name],
      :price => params[:price]
    )
  end
end

Incidentally, unless you're doing something particularly special, it looks like you're probably doing the form in a non-conventional way.

You should be using a form helper along these lines in your view:

<%= form_for @product do |f| %>
  ...

And then in your controller, creating the product as follows:

def create
  @product = Product.new(params[:product])

  if @product.save
    ...
end

UPDATE: As pointed out by @Iceman, if you're using Rails 4 you'll need to use Strong Parameters for the params used for mass-assignment.

Typically you'd create a private method to handle these, and call that within your object creation/update method calls:

class ProductsController < ApplicationController
  def create
    @product = Product.new(product_params)

    if @product.save
      ...
  end

  private

  def product_params
    params.require(:product).permit(:name, :price)
  end
end

edited Jul 2, 2014 at 5:41

answered Jul 1, 2014 at 22:20

Jon

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1 Comment

Eyeslandic Over a year ago

You'll need strong_parameters if this is Rails 4.

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