Documentation / @zerotal/flow / index / param

Function: param()

Call Signature

param(value, context): void

Fills a field from the matched route segment before onMount() runs — including a route-model binding, so a page on /posts/:post receives the loaded Post without querying for it.

Parameters

value

unknown

context

ClassFieldDecoratorContext

Returns

void

When configured, a field decorator; when used bare, nothing (applied directly).

Remarks

Usable bare as @param (the field's own name is the segment), as @param('slug') to read a differently-named segment, or as @param(Post) to take whichever segment resolved to an instance of that model — so the field never has to track what a route called it. One model claims one segment name, so the token form is unambiguous for anything binding implicitly; a route that hand-binds a second segment to the same model yields the leftmost.

Seeding happens once, on the initial GET — the only request that carries the URL's segments. On subsequent WebSocket actions the value is restored from the snapshot instead (a model through Flow's model synth), so pair it with @locked and the record is never re-queried.

@param registers the binding only; combine it with @locked for server-owned data, or @expose if the client may also write it. Applies to a field.

Example

class PostDetailPage extends Component {
  @locked @param post!: Post;           // /posts/:post -> the bound Post
  @locked @param(Post) article!: Post;  // whichever segment resolved to a Post
  @locked @param("tab") activeTab = ""; // /posts/:post/:tab -> the raw segment
}

Call Signature

param(source?): ParamDecorator

Defined in: flow/src/decorators.ts:906