Need a self. method on a Rails model using Acts_as_list

Question

I am still newer to Rails... I need to write a self.method on my Product model to find the next Product per position. I am showing 1 Product on a page, and want the next one in the list.

def self.next_product
product = Product. # current product.position +1
end

obviously this won't work... I am still new to writing methods. anyone?

I am using Rbates Railscast 147 and Acts_as_list, I need to figure out how to get the next product

thanks so much

Answer 1

acts_as_list already adds methods for getting the next and previous items, they are called higher_item (position - 1) and lower_item (position + 1). However, they are instance methods, not class methods (self.) because to find "the next item" in a list, you need to start with an item (an instance of the Product class), not the Product class itself.

=> p = Product.first
<Product id: 1, position: 1>
=> p.lower_item
<Product id: 2, position: 2>

• See the acts_as_list documentation for descriptions of the methods it adds to your class.
• See this blog post for a description of class and instance methods in Ruby.

Answer 2

class Product
 def next_product
   lower_item or self
 end
 def previous_product
   higher_item or self
 end
end

link_to "Next", product_path(@product.next_item) 

link_to "Previous", product_path(@product.previous_item)