CODEWITHSUNDEEP
ruby-on-rails-5
Kyle Ratliff
Kyle Ratliff

Reputation: 598

Ruby on Rails 5.2 Upgrade | ArgumentError (A class was passed to `:class_name` but we are expecting a string.)

I am upgrading a Ruby on Rails application to 5.2 from 5.0 and am receiving this error when attempting to call any of my models that have a relationship defined:

ArgumentError (A class was passed to :class_name but we are expecting a string.)

Code causing issues

  belongs_to :manufacturer,
             foreign_key: :org_id_mnfr,
             class_name: Organization::Manufacturer

Upvotes: 1

Views: 731

Answers (1)

Kyle Ratliff
Kyle Ratliff

Reputation: 598

The issue is with the new Rails version. Rails 5.2 no longer accepts non-quoted class names with the class_name: attribute. You need to change all instances in which class_name: is being passed an actual model, rather than a string of the model name.

eg. Organization::Manufacturer becomes 'Organization::Manufacturer'

If your application has many instances of this as mine did, you will probably want a way to automatically change these. Here is how I used Atom editor and Regex to find and replace all instances of this.

Find All with Regex Enabled:

Find in project: class_name: ([^'][\w|:]*[^'|,| |\n])

Replace With: class_name: '$1'

File/Directory Pattern *.rb

What this is doing: Find all instances of class_name that are not already quoted and capture the Class name within capture group 1. We then replace the entire find by with the static string class_name: and then the first capture group with single quotes around it.

This results in: class_name: Organization::Manufacturer becoming class_name: 'Organization::Manufacturer'

This can handle the class name attribute having a space , a new line \n, or a comma , character after. But there may be some instances in which this causes errors so please double check the replaces before hitting Commit!

Upvotes: 5

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