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Quick Start

Create a `.ddd` File

Create registration.ddd:

context Registration {

  type UserId = String
  type Email = String
  type DisplayName = String
  type Reason = String

  command Register {
    userId: UserId
    email: Email
    name: DisplayName
    validate email != ""
      else "Email must not be empty"
    validate name != ""
      else "Display name must not be empty"
  }

  command Deactivate {
    userId: UserId
    reason: Reason
  }

  event Registered {
    userId: UserId
    email: Email
    name: DisplayName
  }

  event Deactivated {
    userId: UserId
    reason: Reason
  }

  decider User {
    commands: Register, Deactivate
    events: Registered, Deactivated
    state: Unregistered | Active(email: Email, name: DisplayName) | Inactive(reason: Reason)
    initial: Unregistered
    terminal: Inactive

    decide(Register, Unregistered) -> [Registered { userId, email, name }]

    decide(Deactivate, Unregistered) -> impossible "Cannot deactivate an unregistered user"

    decide(Register, Active) -> already "User is already registered"

    decide(Deactivate, Active) -> [Deactivated { userId, reason }]

    evolve(Unregistered, Registered) -> Active
    evolve(Unregistered, Deactivated) -> Inactive
    evolve(Active, Registered) -> Active
    evolve(Active, Deactivated) -> Inactive

  }
}

What This Describes

A context named Registration (a bounded context)
A command Register carrying user data
An event Registered recording what happened
A decider User with two states: Unregistered and Active

The decider accepts Register only when Unregistered, produces a Registered event, and transitions to Active.

Validate

weltenwanderer validate registration.ddd

Output on success:

✓ registration.ddd

The validate command accepts one or more glob patterns and reports errors with line:col positions.

Generate Code

weltenwanderer generate registration.ddd --target emmett

The generate command uses the Emmett code generator to produce TypeScript output. See Code Generation for details on the generated file structure.