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ModalVM

When To Use It

Use ModalVM when a modal interaction should be represented as a VM-backed result that host services can present and await. It fits domain-specific modal flows that do not belong in the fixed PickFile*, Confirm, or Notify methods on IDialogService.

Shape And Ownership

The core contract is small:

  • cancellation result
  • eventual result
  • dismissed flag
  • awaitable completion
  • idempotent dismiss and dispose

Swift exposes the contract as ModalVM plus the concrete BasicModalVM<Result> helper; the other flavors ship ModalVM<T> directly.

Lifecycle And Messaging

Modal completion is single-winner and host-driven:

  • Dismiss(result) completes the modal exactly once
  • Dispose() completes it with the cancellation result
  • null dialog presentation returns the cancellation result immediately
  • awaiters never hang if the modal is disposed instead of explicitly dismissed

Cross-Language Surface

Concept C# Python TypeScript Swift
Concrete helper ModalVM<T> ModalVM[T] ModalVM<T> BasicModalVM<Result>
Awaitable result Completion wait_result() completion waitResult()
Dismiss method Dismiss(...) dismiss(...) dismiss(...) dismiss(...)

Example

The Notes Workspace adapters mostly use the closed Confirm and Notify dialog-service methods, but the modal primitive is the extension point behind IDialogService.Present(...).

Relevant shipped surfaces:

  • C#: VMx.Dialogs.ModalVM<T> and NullDialogService.Present(...)
  • Python: vmx.dialogs.ModalVM
  • TypeScript: src/dialogs/modalVM.ts
  • Swift: ModalVM protocol plus BasicModalVM<Result>

Use this primitive when you need a VM-backed modal result instead of a fixed host dialog verb.

var modal = new ModalVM<string>("cancel");
modal.Dismiss("save");
var result = await modal.Completion;

modal = ModalVM[str]("cancel")
modal.dismiss("save")
result = await modal.wait_result()

const modal = new ModalVM("cancel");
modal.dismiss("save");
const result = await modal.completion;

let modal = BasicModalVM<String>(cancellationResult: "cancel")
modal.dismiss("save")
let result = await modal.waitResult()

Common Pitfalls

  • Reaching for a modal VM when Confirm, PickFileToOpen, PickFileToSave, or Notify already matches the interaction.
  • Forgetting that disposal is a completion path, not just cleanup.
  • Assuming Swift's concrete helper is named exactly like the protocol. The helper is BasicModalVM.