ViewSet Data Access

api.BaseViewSet does not require its Queryset to implement a fixed Go interface. It finds the methods it needs by name when a request arrives. To keep a mistake there from becoming a 500 on the first request, the router checks every viewset's data access when you register it and again when you mount its routes. A viewset that cannot serve its routes stops the application at startup, with a message that names the resource and the missing or mismatched operation.

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Operations by action

Queryset holds a manager (anything with the write methods below, such as orm.Manager[T]) or, for a read-only resource, any value with the read methods. Model must be a non-nil pointer to the model struct, for example &Product{}.

Action	Route	Operation on Queryset
list	GET /resource/	Count(context.Context) (int64, error) and All(context.Context) ([]T, error)
retrieve	GET /resource/{id}	Get(context.Context, int64) (*T, error)
create	POST /resource/	Create(context.Context, *T) error
update, partial_update	PUT/PATCH /resource/{id}	Get, then Update(context.Context, *T) error
destroy	DELETE /resource/{id}	Get, then Delete(context.Context, *T) error

The parameter types can be wider than shown. *T can be interface{}, and the context parameter can be any interface that context.Context satisfies. All can return any slice. The object Get returns is what Update and Delete receive, so their parameter must accept it. On a writable resource, Get must return a pointer or an interface, because the viewset populates that object in place.

List pipeline

list calls these optional methods when they exist. If a method is present, its signature must match:

Method	Signature	Used for
Filter	Filter(orm.Expression) Q (the parameter may be any interface that orm.Expression satisfies)	?field=value filters
OrderBy	OrderBy(...string) Q (...any also works)	?ordering= and the default order
Offset, Limit	Offset(int) Q, Limit(int) Q	pagination

If the Queryset lacks Offset or Limit but has a QuerySet() constructor that takes no arguments, list runs against that constructor's result. That is how orm.Manager[T] paginates in SQL: Count, All, Filter, OrderBy, Offset and Limit are checked on orm.QuerySet[T].

orm.Manager[T], the <Model>Objects managers that forge generate emits, and the generated <Model>ViewSet all pass the check.

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Read-only resources

A resource that should only be listed and retrieved sets ReadOnly:

vs := api.NewBaseViewSet(NewReportSerializer, ReportObjects, &Report{})
vs.ReadOnly = true
router.Register("reports", vs)

A read-only viewset needs only Count, All and Get. POST, PUT, PATCH and DELETE respond 405 Method Not Allowed with Allow: GET. Those responses come after authentication, permission and throttle checks, and they never call the queryset. ViewSetConfig has the same ReadOnly field.

A writable viewset whose queryset has no Create, Update or Delete fails the check, and the message suggests ReadOnly.

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When the check runs

• Router.Register checks the viewset and panics if the check fails.
• Router.RegisterRoutes checks every registered viewset again before it mounts any route, so a field changed after Register is also caught.

Both calls panic because the problem is a programming error that no request can recover from. This matches Router.Action, which panics on an unknown HTTP method, and http.ServeMux.Handle, which panics on an invalid pattern. To get the problem as an error instead, for example in a test, call CheckConfiguration() on the viewset.

The check reports every problem at once:

api: resource "reports": Queryset *reports.Store: missing Create(context.Context, *Model) error, needed by create; Queryset *reports.Store: missing Update(context.Context, *Model) error, needed by update and partial_update; Queryset *reports.Store: missing Delete(context.Context, *Model) error, needed by destroy; set ReadOnly to serve only list and retrieve

Messages contain the resource name, Go type names and operation names. They never contain configured values, so a connection string held by a queryset does not reach logs or crash reports.

Beyond the operations, the check rejects a nil or typed-nil viewset, a nil serializer factory or one that returns nil or panics, a nil Model, a typed-nil Model such as (*Product)(nil), a Model that is not a pointer to a struct, and a nil or typed-nil Queryset.

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Custom viewsets

• A type that implements api.ViewSet without embedding *api.BaseViewSet is checked only for nil. Its handlers own their data access.
• A type that embeds *api.BaseViewSet inherits CheckConfiguration, so the embedded viewset is checked. If the type serves some actions from its own data, define CheckConfiguration() error on it to state its real requirements, or return nil.
• api.ViewSetConfig checks that Serializer is set, then checks the viewset it would build. The check does not build or cache that viewset, so fields you set after Register still apply.