Queries

Queries are read-side entry points. A query maps to a return type — a read model, or a collection of read models with [].

Syntax

query <Name> => <ReturnType>[[]?]
  [by <paramName> <Type>]
  [filter <paramName> <Type>?]
  [authorize <PolicyName> [or <PolicyName>]*]

Clause	Meaning
by	The identifying parameter — the query returns the instance it identifies.
filter	An optional parameter narrowing the result set. Filter types are typically optional (?).
authorize	The policies that must pass.

Examples

A single-instance query identified by a parameter:

query GetInvoice => InvoiceDetailsReadModel
  by invoiceId InvoiceId
  authorize IsAuthenticated

A collection query with optional filters:

query ListInvoices => InvoiceListReadModel[]
  filter status     InvoiceStatus?
  filter customerId CustomerId?
  authorize IsAuthenticated

Guidance

• Name queries as descriptive reads: GetInvoice, ListInvoices, GetOverdueInvoices.
• The return type is a read model built by a projection in the same or another StateView slice.
• Screens bind to queries with data <ReadModel> via query <QueryName>.