Hey guys just trying to figure out why this does not work. Basically this relationship does
belongs_to :product_category, :foreign_key => :category_id
And this one does not
belongs_to :category, :class_name => :product_category, :foreign_key => :category_id
The error message is "NameError: uninitialized constant product::product_category"
Why is that? Thanks!
The latter example does not work because there is no class called product_category. You are providing the wrong class name. Class names in Ruby should be written in CamelCase. When Rails looks for a product_category class it's not going to find it.
Your first example works because Rails infers the name of the class from the name of the relationship.
belongs_to :product_category, :foreign_key => :category_id
It converts product_category to ProductCategory. You can do the same thing yourself. Open up a terminal and type the following.
'product_category'.camelize.constantize
You should pass in a string instead:
belongs_to :category, :class_name => 'ProductCategory', :foreign_key => :category_id
But in this case it would be redundant since Rails can already infer the class name. The class_name argument should be used when the class name can not be inferred from the relationship name.