Hyrax v3.0 ( branch: )

Change Sets

To understand Change Sets, see Dive into Valkyrie tutorial.

Change Sets and Hyrax

Hyrax automatically creates change sets for new/edit forms. See New/Edit Forms section for more information.

Custom Change Sets Use Case

We define 2 work types: PublicationResource and ReleaseResource. A release can be in one and only one publication. The publication uses attribute member_ids to link to releases. The release uses attribute publication_id as a link to the publication. To support this, we have method ReleaseResource #move_to_new_publication which changes 3 resources: the release, the old publication, and the new publication.

To support this, a change set was defined for publications and releases.

class PublicationResourceChangeSet < Hyrax::ChangeSet
  validates :title, presence: true
end

class ReleaseResourceChangeSet < Hyrax::ChangeSet
  validates :title, presence: true
  validates :publication_id, presence: true
end

The basic move process is…

  • instantiate a change set for all 3 resources
  • in the old publication change set, remove the release id from the old publication’s member_ids
  • in the new publication change set, add the release id to the new publication’s member_ids
  • in the release change set, set the release’s publication id to the new publication id
  • validate all 3 change sets
    Example… 
      release_change_set.valid?
  • if validations pass, use UpdateWork transaction to sync each change set and save the resources
    Example… 
      Hyrax::Transactions::UpdateWork.new.call(release_change_set).or do |failure|
    raise "Unable to save release #{change_sets[:self_change_set].title}; " \
          "CAUSE: #{failure.first}"
  end
  • The UpdateWork transaction calls valid? on the resource being updated, so why do I call valid? before executing the transactions?

    Transactions are not reversible. When executing multiple transactions, if one passes and a later one fails, this may cause an invalid state. In an attempt to mitigate this, valid? is called on all 3 resources before calling UpdateWork transaction on each.