Status Constraints
Status Constraints are constraints over the Primary state when it is a particular status.
They are shown as a rounded box under the status state box to which the constraints apply:
In the Agreement example use case, status constraints are used to show which state properties must be populated for a particular status. In particular, the aim is to:
- Mandate that rejectionReason and rejectedBy are set to null when in the PROPOSED status.
- Mandate that rejectionReason and rejectedBy are filled in when in the REJECTED status.
Whether the fields should be null or populated in the AGREED status has not been specified.
When using Kotlin types, fields cannot be null unless they are marked as nullable with a ‘?’ after the type, eg rejectionReason: String?. So there is no need to specify that a non-nullable field, eg buyer: Party must be populated, it is implied in the class type. Although in the example, we have stated it explicitly anyway.