Fix error: NoMethodError (MAYBE-MARKETING-8)

[revise-dev]

The error NoMethodError: undefined method 'symbol' for nil:NilClass occurs when we try to call the symbol method on a nil object. In this case, it's happening because the @stock variable is nil, which means the Stock.find_by(symbol: params[:ticker]) query didn't find a matching stock.

To fix this, we need to use the find_by! method instead of find_by. The bang version (find_by!) will raise an ActiveRecord::RecordNotFound exception if no record is found, rather than returning nil. This is preferable because:

1. It prevents the NoMethodError from occurring further down in the view.
2. It automatically triggers Rails' standard 404 handling, which is more appropriate for a record that doesn't exist.
3. It makes the code's intent clearer - we expect this record to exist, and if it doesn't, it's an exceptional case.

Here's a detailed explanation of the change:

1. We replace find_by with find_by! in the show action of the StocksController.
2. This change will now raise an ActiveRecord::RecordNotFound exception if no stock is found with the given ticker symbol.
3. Rails will automatically catch this exception and render a 404 Not Found response, which is the correct behavior when a requested resource doesn't exist.
4. This prevents the error from bubbling up to the view, where it was previously trying to call symbol on a nil object.

This change maintains the original intent of the code (finding a stock by its ticker symbol) while adding a layer of error handling that improves the user experience and application robustness.

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[Shpigford]

/revise write tests for this as well

[revise-dev]

To address the comment "write tests for this as well", we need to add tests for the StocksController, specifically for the show action. We'll create a new test file spec/controllers/stocks_controller_spec.rb (assuming RSpec is being used for testing).

The tests will cover two scenarios:

1. When a valid stock ticker is provided, it should return a successful response and assign the correct stock.
2. When an invalid stock ticker is provided, it should raise an ActiveRecord::RecordNotFound exception.

These tests will ensure that our controller behaves correctly both for existing and non-existing stocks, validating the change we made to use find_by!.

Updated files:

• spec/controllers/stocks_controller_spec.rb
• app/controllers/stocks_controller.rb