On Jan 25, 2015, at 3:42 PM, Maxim Chernyak <madfanc...@gmail.com> wrote:
> When using STI, if you introduce a new subclass in a git branch, then create > a db record while in it, then switch to another branch, you will get > uninitialized constant error when trying to query those records. Certain > kinds of applications (like ours) could run into this a lot, so I'm wondering > if there could be a null-object-patternish solution to this. E.g: > > * Accept proc for inheritance_column, which evaluates on instances, with type > passed as an arg to it, and whatever it returns becoming the record in that > case. This way we can plug those records with some placeholders The proc can’t be run on an instance - the error is arising when AR tries to determine what class to use. The calling context is in find_sti_class: https://github.com/rails/rails/blob/6d72485b6977804a872dcfa5d7ade2cec74c768e/activerecord/lib/active_record/inheritance.rb#L169 a class method defined on ActiveRecord::Base. At runtime, this will have access to the class that `find` was called on (presumably the STI base class) and the value from the inheritance column. Returning a fully-initialized object from here would require skipping a bunch of code in `instantiate`. > * Add option self.ignore_unknown_types = true to activerecord to simply > auto-rescue + skip records with uninitialized constant error (perhaps print a > warning instead) It’s not clear to me what “skipping” a record in this scenario would mean. If I have a model that belongs_to an instance of the missing class, what do I get back when I access it? `nil`? `RecordNotFound` exception? If I have a validation that requires the presence of that missing object, does `save` still work? There are plenty more questions like those. “Muddling through” with bad data is almost certainly going to break something upstream in people’s applications - something considerably harder to troubleshoot than a straightforward `SubclassNotFound` error on loading a bad record. As to the “sample data” issue, if it’s worth keeping in the DB it’s worth keeping in source control. If writing a db/seeds.rb file is too complicated (maybe you’re importing large datasets from elsewhere), I’d recommend things like YamlDb to make repeatable seed data. Even `mysqldump > sample_data.sql` is a start… —Matt Jones -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Core" group. To unsubscribe from this group and stop receiving emails from it, send an email to rubyonrails-core+unsubscr...@googlegroups.com. To post to this group, send email to rubyonrails-core@googlegroups.com. Visit this group at http://groups.google.com/group/rubyonrails-core. For more options, visit https://groups.google.com/d/optout.
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