debugging a ruby on rails error

I'm some what new with ruby on rails, so I'm attempting to debug this error that I'm getting but, from my understanding, is working on the prod code.

The error:

NoMethodError in Jo开发者_JAVA技巧inController#index
undefined method `join_template' for nil:NilClass
/app/controllers/join_controller.rb:5:in `index'

Okay, so line 5 in index is:

elsif current_brand.join_template == 'tms'

So clearly current_brand is nil. The controller is a child class of AppController, so checking that out I see that current_brand is a method:

  def current_brand
    return @current_brand if defined?(@current_brand)
    url_array = request.env['HTTP_HOST'].split('.').reverse
    url = url_array[1] << "." << url_array[0]
    @current_brand = Brand.find(:first, :conditions => ["url LIKE ?", "%" << url << "%"])
  end

It seems that @current_brand is always returned, yet it's continuing to be Nil. What could the problem be?

It may be your query is not returning anything. You can use a debugger, but it's pretty easy to just output @current_brand and see what it evaluates to.

logger.debug(@current_brand)

You must check two things:

1. Does Rails build the SQL query properly with the url passed in on the last line of that method?
2. Does the record exist in the brands table? you're not actually checking for that.

Also, passing in the url like that opens you up to a potential SQL injection attack.

You need to rewrite your definition with a rescue or if/else so if you do get a nil element then it won't be a fatal error.

This is your problem:

@current_brand = Brand.find(:first, :conditions => ["url LIKE ?", "%" << url << "%"])

@current_brand is not finding anything so make sure you find something.

@current_brand = Brand.find(:first)

If this fixes the problem then you know it is not finding anything and you will need to change your code that if it returns nil then it doesn't provide the function or it finds a default brand such as what I suggested.