Activate - Sequence ID

# ID Sequences

You can provide a `Sequence` for your `Entities` in order to alter generated ID's from default UUID's.

The traits you can use:

```
trait Entity extends BaseEntity with UUID
trait EntityWithCustomID[ID] extends BaseEntity with CustomID[ID]
trait EntityWithGeneratedID[ID] extends BaseEntity with GeneratedID[ID]
```

## ID Generators

```
abstract class IdGenerator[E <: BaseEntity: Manifest]

abstract class SegmentedIdGenerator[E <: BaseEntity: Manifest](
    fSequence: => Sequence[E#ID])(
        implicit n: Numeric[E#ID],
        ctx: ActivateContext)
        extends IdGenerator[E]

abstract class SequencedIdGenerator[E <: BaseEntity: Manifest](
    val sequence: Sequence[E#ID])
        extends IdGenerator[E] {
    def nextId =
        sequence.nextValue(1)
```

> SegmentedIdGenerator should be used if the id doesn't need to be strictly sequencial.

There are two built in sequences in `net.fwbrasil.activate.sequence`:

- IntSequenceEntity
- LongSequenceEntity

## Example

```
class ModelIDSequence(name: String)
  extends SequenceEntity[String](name, 1) {
  def _nextValue = {
    value += step
    s"$name%05d" format value
  }
}

object ModelIDSequence {
  def apply(sequenceName: String, step: Int = 1) = {
    transactional(requiresNew) {
      select[ModelIDSequence].where(_.name :== sequenceName).headOption.getOrElse {
        new ModelIDSequence(sequenceName)
      }
    }
  }
}

class ModelSID extends SequencedIdGenerator[Model](ModelIDSequence("m"))
```

> The above ModelSID will be bind to the Model Entity.