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Define data models for Fabric Apps

Fabric Apps uses TypeScript decorators to define data models that generate database tables and APIs. You define each entity as a class decorated with @entity(), add field decorators for data types, and map relationships between entities.

For authorization and access control guidance, see Define data permissions.

Prerequisites

  • A Fabric Apps project created with npm create @microsoft/rayfin@latest or initialized with npx rayfin init.
  • Basic understanding of TypeScript classes and decorators.

Define an entity

To create a data model, add the @entity() decorator to a TypeScript class. Then import the required decorators from @microsoft/rayfin-core:

import { entity, uuid, text, date } from '@microsoft/rayfin-core';

@entity()
export class Todo {
  @uuid() id!: string;
  @text() title!: string;
  @text({ optional: true }) description?: string;
  @date() createdAt!: Date;
  @date() updatedAt!: Date;
}

This entity generates a Todo table with columns for id, title, description, createdAt, and updatedAt.

Primary keys

Every entity uses a UUID string field named id as its primary key. If you don't declare id explicitly, Fabric Apps adds it to the schema automatically.

  • The id field is optional during create operations—the server generates a UUID if you omit it.
  • You can supply your own UUID at creation time if you prefer client-generated identifiers.
  • Composite primary keys and custom key names aren't supported.
@entity()
export class Note {
  @uuid() id!: string;  // UUID primary key, auto-generated when omitted
  @text() title!: string;
  @text() content!: string;
}

Supported data types

Use these decorators to define field types:

Decorator Type Description
@uuid() string Unique identifier field.
@text() string Text field with optional length constraints.
@int() number Integer field.
@decimal() number Decimal or numeric field.
@boolean() boolean True or false field.
@date() Date Date and time field, serializes from ISO strings or Date objects.
@email() string Text field with email validation.
@set() string Enumerated set of string literals.

Example with multiple types

import { entity, uuid, text, int, decimal, boolean, date, set } from '@microsoft/rayfin-core';

@entity()
export class Product {
  @uuid() id!: string;
  @text() name!: string;
  @decimal() price!: number;
  @int() stockQuantity!: number;
  @boolean() isAvailable!: boolean;
  @date() createdAt!: Date;
  @set('draft', 'published', 'archived') status!: 'draft' | 'published' | 'archived';
}

Type modifiers

Add modifiers to field decorators to configure validation and constraints:

Modifier Description
{ optional: true } Allow NULL values. Fields are required by default.
{ unique: true } Add a unique constraint.
{ default: value } Set a default value expression.
{ max: n }, { min: n } String length constraints (maximum and minimum number of characters).
{ min: n }, { max: n } Numeric value constraints.

Note

The TypeScript optional marker (? after a property name) only affects the static TypeScript type. It doesn't make the database column nullable. To make a field nullable, add { optional: true } to the decorator. Use ! to assert that a required field is initialized by the framework.

Example with modifiers

@entity()
export class User {
  @uuid() id!: string;
  @email({ unique: true }) email!: string;
  @text({ min: 3, max: 50 }) username!: string;
  @text({ optional: true, max: 500 }) bio?: string;
  @int({ min: 0, max: 150 }) age!: number;
  @boolean({ default: false }) isVerified!: boolean;
}

Define relationships

Use @one() and @many() decorators to define navigation properties between entities. Fabric Apps auto-generates foreign key columns when you define relationships.

  • One-to-many – Use @many() on the parent and @one() on the child.
  • Many-to-one – Use @one() on the child to reference the parent.
  • Many-to-many relationships aren't supported—use an explicit join entity instead.

Example with one-to-many relationship

import { entity, uuid, text, date, one, many } from '@microsoft/rayfin-core';

@entity()
export class Notebook {
  @uuid() id!: string;
  @text() name!: string;
  @date() createdAt!: Date;
  @many(() => Note) notes?: Note[];
}

@entity()
export class Note {
  @uuid() id!: string;
  @text() title!: string;
  @text() content!: string;
  @date() createdAt!: Date;
  @text() notebook_id!: string;
  @one(() => Notebook) notebook?: Notebook;
}

When you define @one(() => Notebook) on the Note entity, Fabric Apps automatically creates a notebook_id foreign key column. Declare the foreign key field explicitly only if you plan to read or set it in application code.

Foreign key naming convention

When you define a foreign key field, use the {property}_id naming convention:

@entity()
export class Note {
  @uuid() id!: string;
  @text() notebook_id!: string;      // Foreign key field
  @one(() => Notebook) notebook?: Notebook;  // Navigation property
}

Custom foreign key names (foreignKey, targetKey options) aren't supported.

Reference system entities

Fabric Apps doesn't support @one() relationships that point to system entities such as the built-in USER entity. To associate a row with the signed-in user, add a plain user_id field of type @text() and populate it from the auth claims (typically claims.sub):

@entity()
export class Task {
  @uuid() id!: string;
  @text() title!: string;
  @text() user_id!: string;  // System user ID from claims.sub
}

Filter rows by user_id in your role policies to enforce per-user access.

Register entities in the schema

Add all entity classes to rayfin/data/schema.ts so the client can generate GraphQL proxies:

import type { Note } from './Note.js';
import type { Notebook } from './Notebook.js';

export type NotesAppSchema = {
  Note: Note;
  Notebook: Notebook;
};

Update this type whenever you create a new entity.

Apply schema changes

After defining or modifying entities, apply the changes to the database:

  1. Deploy the updated schema to Fabric:

    npx rayfin up db apply

  2. If the schema change includes destructive operations (dropping columns, renaming tables), the CLI warns you and refuses to proceed. Use --force to override the safety check:

    npx rayfin up db apply --force

Note

Using --force can cause data loss. Review the listed operations carefully before proceeding.

Best practices

  • Define foreign key fields only when you need to read or set them in code—Fabric Apps generates them automatically from navigation decorators.
  • Use relative imports with .js extensions in entity files so the emitted ESM JavaScript resolves correctly.
  • For authorization patterns and role-based access, see Define data permissions.

Troubleshooting

Missing relationships

If relationships don't appear in the API, verify that:

  • The navigation decorator (@one() or @many()) is present.
  • The entity is registered in rayfin/data/schema.ts.

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