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Jeckel-Lab Contract

List of interfaces use as contract in other packages or DD projects

This contract includes some strong typings, object relation and psalm validation.

Require *`php >= 7.2.** and **php >= 8.0`**

Documentation for version 2.x (php >= 8.0)

Domain

Domain contract are part of DDD implementation suggestion, it's not required and is not linked to any frameworks.

Identity

Identity are used to define a unique identifier for an Entity or a RootAggregate.

Identity must be:

• immutable
• final
• constructor should be private, use a factory method:
  • new ==> Generate (if possible) a new Identity object with a random value (like UUIDs)
  • from ==> Instantiate Identity from an existing value

See detailed implementation proposal: jeckel-lab/identity-contract

Entity

Entity: main Entity contract

Entity must have an Id implementing the Identity interface.

Don't forget to use @psalm templates

Event

Event are notification about what happened during a use case.

Event must be:

• immutable

DomainEventAware

Entities and root aggregates handle domain events. To facilitate this behaviour, you can use this interface and trait:

• DomainEventAwareInterface
• DomainEventAwareTrait

This interface defines two methods:

• addDomainEvent allow you to register new event occurred during a Use Case.
• popEvent will empty the entity's event list at the end of a use case to dispatch them into an Event Dispatcher.

Just use the interface and trait into your entity:

And if you use the CommandBus pattern, then you can add events to the response easily:

ValueObject

Using ValueObject to embed a value (or group of value for complex types) as an object allow you:

• to use strong typing in the application (a Speed can not be mixed with any random float)
• to embed data validation (be sure that the Speed is always a positive value, is lower than a reasonable value, etc.)

Value object must be defined as:

• immutable (one's instantiated, they should not be modified unless a new instance is created).
• final
• constructor should be private, use the static from method as a factory
• when requesting to ValueObject with same value, from should return the same instance

Think about implementing it like this:

Core

To be completed

Command Dispatcher

To be completed

See detailed implementation proposal: jeckel-lab/command-dispatcher

Query Dispatcher

To be completed

See detailed implementation proposal: jeckel-lab/query-dispatcher

Exceptions

Each layer has it's own Exception interface that extends Throwable:

• Core: CoreException
• Domain: DomainException
• Infrastructure: InfrastructureException
• Presentation: PresentationException

In each layer, when we need to throw an Exception, we create a new class corresponding to the type of Exception. This class must:

• extends one of the SPL exception or another (more generic) exception from the same namespace.
• implements the exception interface of the current layer.