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Shared Projection

Description​

A read-model (Projection) that is part of the Shared Kernel.

Definition Schema​

The definition for a shared_projection component expects the following structure:

{
  "$defs": {
    "ProjectionStateFieldDTO": {
      "properties": {
        "name": {
          "title": "Name",
          "type": "string"
        },
        "type_str": {
          "title": "Type Str",
          "type": "string"
        },
        "default_value_str": {
          "anyOf": [
            {
              "type": "string"
            },
            {
              "type": "null"
            }
          ],
          "default": null,
          "title": "Default Value Str"
        },
        "is_factory": {
          "default": false,
          "title": "Is Factory",
          "type": "boolean"
        }
      },
      "required": [
        "name",
        "type_str"
      ],
      "title": "ProjectionStateFieldDTO",
      "type": "object"
    }
  },
  "example": {
    "description": "Tracks the state of order statuses for projection.",
    "fields": [
      {
        "name": "projection_id",
        "type_str": "ProjectionId"
      },
      {
        "name": "order_id",
        "type_str": "str"
      },
      {
        "name": "status",
        "type_str": "str"
      },
      {
        "default_value_str": "None",
        "name": "last_processed_event_id",
        "type_str": "Optional[str]"
      },
      {
        "default_value_str": "datetime.datetime.now(datetime.timezone.utc)",
        "is_factory": true,
        "name": "last_updated_at",
        "type_str": "datetime.datetime"
      }
    ],
    "name": "OrderStatusProjectionState",
    "projection_abstractions_module": "castlecraft_engineer.abstractions.projection"
  },
  "properties": {
    "name": {
      "description": "Name of the ProjectionState class (e.g., 'OrderStatusProjectionState')",
      "title": "Name",
      "type": "string"
    },
    "description": {
      "anyOf": [
        {
          "type": "string"
        },
        {
          "type": "null"
        }
      ],
      "default": null,
      "description": "Optional description for the class.",
      "title": "Description"
    },
    "fields": {
      "description": "Fields of the projection state dataclass.",
      "items": {
        "$ref": "#/$defs/ProjectionStateFieldDTO"
      },
      "title": "Fields",
      "type": "array"
    },
    "projection_abstractions_module": {
      "default": "castlecraft_engineer.abstractions.projection",
      "description": "Module for ProjectionId, etc.",
      "title": "Projection Abstractions Module",
      "type": "string"
    }
  },
  "required": [
    "name"
  ],
  "title": "ProjectionStateEngineInputDTO",
  "type": "object"
}

Naming and Location Conventions​

Class: PascalCase, typically ends with 'Projection'. File: ${shared_projection_name}.py (based on ${shared_projection_name}). Location: app/domain/shared_kernel/projections.

Example Definition​

{
  "name": "OrderStatusProjectionState",
  "description": "Tracks the state of order statuses for projection.",
  "fields": [
    {
      "name": "projection_id",
      "type_str": "ProjectionId"
    },
    {
      "name": "order_id",
      "type_str": "str"
    },
    {
      "name": "status",
      "type_str": "str"
    },
    {
      "name": "last_processed_event_id",
      "type_str": "Optional[str]",
      "default_value_str": "None"
    },
    {
      "name": "last_updated_at",
      "type_str": "datetime.datetime",
      "default_value_str": "datetime.datetime.now(datetime.timezone.utc)",
      "is_factory": true
    }
  ],
  "projection_abstractions_module": "castlecraft_engineer.abstractions.projection"
}