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Concorde reference — Dynamic path placeholders. Decorators and DataProviderKey paths can include placeholders resolved on the host component at runtime: Doc ID: docs/_misc/dynamic-path. Keywords: Concorde, supersoniks, docs/_misc/dynamic-path, dynamic-path, Dynamic path placeholders, reference, DataProviderKey, ${prop}, {$prop}, "users/${userId}", "api/sessions/${sessionId}/sync", "teams.${teamId}.members", resolveDynamicPath, userId, sessionId, requestAnimationFrame. URL: https://concorde.supersoniks.org/crawl/docs/_misc/dynamic-path.html.

Dynamic path placeholders

Decorators and DataProviderKey paths can include placeholders resolved on the host component at runtime:

Resolution is done by resolveDynamicPath. The root property names (userId, sessionId, …) are watched via requestAnimationFrame (see dynamicPropertyWatch.ts).

Default behaviour (ready / not ready)

Placeholder value Path ready? Inserted segment Notes
undefined no — Wait until defined
null no — Same as undefined
"" yes empty string e.g. sessions//sync — request may still run
0 yes "0" Not treated as “missing”
false yes "false"
42, "alpha" yes "42", "alpha"

When ready: false, decorators do not call the network (for @get / @post / @put / @patch), unsubscribe (@bind / @subscribe), or skip publisher binding (@publish / @handle). The decorated property is often left unchanged or set to undefined (HTTP decorators).

When the placeholder later becomes valid, observers run again and behaviour resumes.

skipEmptyPlaceholder option

Some APIs should not run while an id is still "". Opt in per decorator:

@get(new Endpoint<User, { userId: string }>("users/${userId}"), {
  skipEmptyPlaceholder: true,
})
Option Scope
skipEmptyPlaceholder?: boolean Only empty string '' on a placeholder
Default false "" is inserted into the path (legacy behaviour)
true "" → ready: false, same as null / undefined for that segment

Does not affect 0, false, null, or undefined (nullish stays “not ready” regardless).

Available on:

API Where
@get 2nd or 3rd argument (GetOptions)
@post / @put / @patch PostOptions / ApiSendOptions
@bind / @subscribe BindOptions
@publish 2nd argument PublishOptions
@handle HandleOptions

Per-decorator summary

Decorator ready: false ready: true
@get No HTTP; payload → undefined ApiResult assigned
@post / @put / @patch No HTTP; payload → undefined ApiResult assigned
@subscribe / @bind Unsubscribe; prop keeps last value Subscribe onAssign
@publish Internal publisher null; writes ignored publisher.set on assign
@handle No subscription; with waitForAllDefined, method not called Callback on assign

See also