Counter¶
This example describes the mechanics of counters associated with a specific controller, implemented in a resource model.
CounterId
resource (application)¶
CounterId
resource represents a counter tied to a specific controller that is used to initialise other counters. In a sense, it can be seen as a counter of counters. CounterId
resource can be seen as an atomic counter (in a broad sense) application. For that reason, we describe it in the application terms.
CounterId
application interface¶
- Init: creates a new
CounterId
resource with a zero value. - Update: updates an existing
CounterId
resource from value \(n\) to value \(n + 1\).
CounterId
application logic constraints¶
- The quantity of each
CounterId
resource must be the same, set to a non-zero constant value \(q\). - Each
CounterId
resource must have the controller's public key in the label. - A signature from the controller authorising the transaction must be provided (verified with the key stored in the label).
- Init case: The value (representing the current count) must be set to 0. The transaction must be balanced by a consumed ephemeral resource of the same kind.
- Update case: The value of the created resource must be set to \(n + 1\) where \(n\) is the value of the consumed resource of the same kind.
Counter application¶
Counter resource represents a simple counter.
Counter
application interface¶
- Init: a new counter is initialised from the current counterId resource (the counterId value goes to the counter resource label). When a new counter is created, the
CounterId
resource is updated to ensure there are no counters that have the same label. - Update: An existing
Counter
resource can be updated from value \(n\) to value \(n + 1\).
Counter
application logic constraints¶
- The quantity of each counterId resource must be the same, set to a non-zero constant value \(q\).
- Each
Counter
resource must have the controller's public key in the label and a value of theCounterId
resource from the moment theCounter
resource was initialised. - Init case:
- The label and the value are set to the value of the
CounterId
resource updated in the same transaction function. The transaction must be balanced by a consumed ephemeral resource of the same kind. - The resource kind of the
CounterId
resource must be verified to ensure that this is indeed theCounterId
resource's value is used to derive theCounter
resource label.
- The label and the value are set to the value of the
- Update case:
- The value of the created resource must be set to \(n + 1\) where \(n\) is the value of the consumed resource of the same kind.
In this simple version, updating the counter requires no special permissions but the counter resource logic can be modified to be more complex and have more restricted counter update rules.