Example App

The repository includes a small in-memory NestJS app under examples/books-api. It is modeled after a real resource controller flow, but uses neutral Book, Author, and Tag data instead of application-specific CRM models.

What It Shows

• ResourceQuery.query for paginated list endpoints.
• ResourceQuery.findById for detail endpoints.
• DTO-backed optional fields validation and projection on every controller route.
• paginated envelope projection for items and meta.
• generated includes for author, nested author.books, and tags.
• QueryService with an authorization-aware accessibleWhere resolver.
• CheckPolicies, PoliciesGuard, ApiResourceQuery, ApiPaginatedResponse, ApiErrorResponses, and ApiParamId.
• QueryTransformPipe, FieldsExceptionFilter, and Swagger setup.
• a complete CRUD controller with GET, POST, PATCH, and DELETE.

Run

pnpm examples:check
pnpm examples:build
pnpm examples:start

Swagger is available at:

http://localhost:3000/docs

Use a different port when 3000 is already taken:

PORT=3100 pnpm examples:start

Routes

Query published books:

curl -g 'http://localhost:3000/books?fields=id,title,author{name},tags{name}'

Find one book and request nested author books:

curl -g 'http://localhost:3000/books/book-1?fields=id,title,author{name,books{title}}'

Project a paginated response envelope:

curl -g 'http://localhost:3000/books?fields=items{id,title},meta{page,perPage,itemCount,pageCount}'

Create a book:

POST /books
Content-Type: application/json

{
  "title": "Composable Nest APIs",
  "isbn": "978-0000000004",
  "authorId": "author-ada",
  "tagIds": ["tag-nest", "tag-api"]
}

Delete a book:

DELETE /books/book-2?fields=id,title

Update a book:

PATCH /books/book-2
Content-Type: application/json

{
  "title": "Typed Prisma Services, 2nd Edition",
  "tagIds": ["tag-prisma", "tag-api"]
}

Every route accepts fields. Unknown DTO fields return HTTP 400 during fields validation. Invalid select and include keys return HTTP 400 in the demo delegate, matching the error surface a Prisma-backed QueryService exposes.

Source Layout

File	Purpose
books/book.dto.ts	Public DTOs and in-memory model types.
books/book.delegate.ts	Prisma-like in-memory delegate consumed by QueryService.
books/books.service.ts	QueryService subclass with demo access filtering.
books/books.controller.ts	CRM-style controller using ResourceQuery and decorators.
main.ts	Swagger, fields errors, and query transformation bootstrap.

See the complete NestJS main.ts and CRUD Controller examples for copyable versions.