Signal Forms Architecture

The packages/forms/signals directory contains an experimental, signal-based forms API for Angular. This system differs significantly from the existing Reactive and Template-driven forms.

Mental Model

1. Model-Driven: The system is built around a WritableSignal<T> which serves as the single source of truth. Unlike Reactive Forms where the FormControl holds the value, here the Signal holds the value. The form is merely a view or projection of that signal, adding form-specific state (validity, dirty, touched).

2. Proxy-Based Traversal: The form API (form(signal)) returns a FieldTree. This object is a Proxy. It allows accessing nested fields (e.g., myForm.user.name) without manually creating control groups. Accessing a property on the proxy lazily resolves or creates the corresponding FieldNode.

3. Schema-Based Logic: Validation, disabled state, and other metadata are defined separately via Schemas. Schemas are applied to the form structure using functions like apply, applyEach (for arrays), and applyWhen. This separates the structure of the data from the rules governing it.