46 lines
1.5 KiB
Ruby
46 lines
1.5 KiB
Ruby
# Include atomic internal id generation scheme for a model
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#
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# This allows us to atomically generate internal ids that are
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# unique within a given scope.
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#
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# For example, let's generate internal ids for Issue per Project:
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# ```
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# class Issue < ActiveRecord::Base
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# has_internal_id :iid, scope: :project, init: ->(s) { s.project.issues.maximum(:iid) }
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# end
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# ```
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#
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# This generates unique internal ids per project for newly created issues.
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# The generated internal id is saved in the `iid` attribute of `Issue`.
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#
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# This concern uses InternalId records to facilitate atomicity.
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# In the absence of a record for the given scope, one will be created automatically.
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# In this situation, the `init` block is called to calculate the initial value.
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# In the example above, we calculate the maximum `iid` of all issues
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# within the given project.
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#
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# Note that a model may have more than one internal id associated with possibly
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# different scopes.
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module AtomicInternalId
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extend ActiveSupport::Concern
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module ClassMethods
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def has_internal_id(column, scope:, init:) # rubocop:disable Naming/PredicateName
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before_validation(on: :create) do
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if read_attribute(column).blank?
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scope_attrs = { scope => association(scope).reader }
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usage = self.class.table_name.to_sym
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new_iid = InternalId.generate_next(self, scope_attrs, usage, init)
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write_attribute(column, new_iid)
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end
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end
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validates column, presence: true, numericality: true
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end
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end
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def to_param
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iid.to_s
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end
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end
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