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Diffstat (limited to 'app/models/concerns/atomic_internal_id.rb')
| -rw-r--r-- | app/models/concerns/atomic_internal_id.rb | 46 |
1 files changed, 46 insertions, 0 deletions
diff --git a/app/models/concerns/atomic_internal_id.rb b/app/models/concerns/atomic_internal_id.rb new file mode 100644 index 00000000000..4b66725a3e6 --- /dev/null +++ b/app/models/concerns/atomic_internal_id.rb @@ -0,0 +1,46 @@ +# Include atomic internal id generation scheme for a model +# +# This allows us to atomically generate internal ids that are +# unique within a given scope. +# +# For example, let's generate internal ids for Issue per Project: +# ``` +# class Issue < ActiveRecord::Base +# has_internal_id :iid, scope: :project, init: ->(s) { s.project.issues.maximum(:iid) } +# end +# ``` +# +# This generates unique internal ids per project for newly created issues. +# The generated internal id is saved in the `iid` attribute of `Issue`. +# +# This concern uses InternalId records to facilitate atomicity. +# In the absence of a record for the given scope, one will be created automatically. +# In this situation, the `init` block is called to calculate the initial value. +# In the example above, we calculate the maximum `iid` of all issues +# within the given project. +# +# Note that a model may have more than one internal id associated with possibly +# different scopes. +module AtomicInternalId + extend ActiveSupport::Concern + + module ClassMethods + def has_internal_id(column, scope:, init:) # rubocop:disable Naming/PredicateName + before_validation(on: :create) do + if read_attribute(column).blank? + scope_attrs = { scope => association(scope).reader } + usage = self.class.table_name.to_sym + + new_iid = InternalId.generate_next(self, scope_attrs, usage, init) + write_attribute(column, new_iid) + end + end + + validates column, presence: true, numericality: true + end + end + + def to_param + iid.to_s + end +end |