Exception: Mongoid::Errors::UnrecognizedModelAlias

Inherits:
MongoidError
  • Object
show all
Defined in:
lib/mongoid/errors/unrecognized_model_alias.rb

Overview

Raised when a polymorphic association is queried, but the type of the association cannot be resolved. This usually happens when the data in the database references a type that no longer exists.

For example, consider the following model:

class Manager
  include Mongoid::Document
  belongs_to :unit, polymorphic: true
end

Imagine there is a document in the ‘managers` collection that looks something like this:

{ _id: ..., unit_id: ..., unit_type: 'Department::Engineering' }

If, at some point in your refactoring, you rename the ‘Department::Engineering` model to something else, Mongoid will no longer be able to resolve the type of this association, and asking for `manager.unit` will raise this exception.

To fix this exception, you can add an alias to the model class so that it can still be found, even after renaming it:

module Engineering
  class Department
    include Mongoid::Document

    identify_as 'Department::Engineering'

    # ...
  end
end

Better practice would be to use unique strings instead of class names to identify these polymorphic types in the database (e.g. ‘dept’ instead of ‘Department::Engineering’).

Constant Summary

Constants inherited from MongoidError

MongoidError::BASE_KEY

Instance Attribute Summary

Attributes inherited from MongoidError

#problem, #resolution, #summary

Instance Method Summary collapse

Methods inherited from MongoidError

#compose_message

Constructor Details

#initialize(model_alias) ⇒ UnrecognizedModelAlias

Returns a new instance of UnrecognizedModelAlias.



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# File 'lib/mongoid/errors/unrecognized_model_alias.rb', line 43

def initialize(model_alias)
  super(
    compose_message(
      'unrecognized_model_alias',
      model_alias: model_alias.inspect
    )
  )
end