A Global ID is a URI that uniquely identifies a model instance:

gid://YourApp/Some::Model/id

This is helpful when you need a single identifier to reference different classes of objects.

One example is job scheduling. We need to reference a model object rather than serialize the object itself, so we pass a Global ID that can be used to locate the model when it's time to perform the job. The job scheduler needn't know the details of model naming and IDs, just that it has a global identifier that references a model.

Another example is a drop-down list of options with Users and Groups. Normally we'd need to come up with our own ad hoc scheme to reference them. With Global IDs, we have a universal identifier that works for objects both classes.

Mix GlobalID::Identification in to any model with a #find(id) class method. Support is automatically included in Active Record.

>> person_gid = Person.find(1).global_id
=> #<GlobalID ...

>> person_gid.uri
=> #<URI ...

>> person_gid.to_s
=> "gid://app/Person/1"

>> GlobalID::Locator.locate person_gid
=> #<Person:0x007fae94bf6298 @id="1">

GlobalID is released under the MIT license.