Question 1

How to add custom async validation in Reactive Forms?

Accepted Answer

Define an async validator class extending AsyncValidator or use Validators.delegateAsync(), then add it to a FormControl's asyncValidators list. The README shows an example with debounce control for checking email uniqueness against a server.

Question 2

Reactive Forms vs Flutter's built-in Form: which is better for dynamic fields?

Accepted Answer

Reactive Forms excels with dynamic fields via FormArray, allowing programmatic control addition/removal, while Flutter's Form is more manual. For complex, changing forms, Reactive Forms reduces boilerplate and handles validation seamlessly.

Question 3

How to handle nested FormGroups for multi-step wizards?

Accepted Answer

Declare nested FormGroups within a parent FormGroup, as shown in the README's 'Groups of Groups' section. Use dot notation (e.g., 'address.city') to access controls, enabling structured data collection for wizards or complex layouts.

Question 4

Why are validation messages not showing up in my ReactiveTextField?

Accepted Answer

Messages appear only when a control is invalid and touched; mark controls as touched initially or use markAsTouched() after setting values. Override showErrors in widgets if needed, as detailed in the 'When do Validation Messages Appear?' section.

Question 5

How to integrate Reactive Forms with Provider state management?

Accepted Answer

Use the reactive_forms_provider plugin or wrap forms in a Provider context, storing FormGroup in a ChangeNotifier. The README mentions compatibility with Provider for state management integration in forms.

Question 6

Best way to disable a form field based on another field's value?

Accepted Answer

Listen to value changes using ReactiveValueListenableBuilder or form control events, then call markAsDisabled() on the dependent control. This requires manual logic, as cross-control enabling isn't built-in but is flexible via the model.

@joanpablo/reactive_forms

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