How do you pass data with Navigator.push and return data with Navigator.pop?
Navigator.push<T> returns a Future for the value supplied to Navigator.pop. Pass data into the destination constructor, await a nullable result, and check mounted before using the parent context after the await.
Navigator.push<T> returns a Future<T?> that completes when the route is popped. Pass input through the destination constructor, return the selected value from the child, and handle a null result when the route is dismissed.
Example
This fragment goes inside a State method. locale is existing state, and LanguagePicker accepts initialLocale.
final Locale? picked = await Navigator.push<Locale>(
context,
MaterialPageRoute<Locale>(
builder: (_) => LanguagePicker(initialLocale: locale),
),
);
if (!context.mounted || picked == null) return;
setState(() => locale = picked);
// In LanguagePicker, after the user chooses a locale:
Navigator.pop(context, const Locale('es'));Watch out for
The Future-based handshake suits a small parent-child interaction. A declarative router or shared state may fit a larger flow. After any await, check that the context is still mounted before using it.
Interview question
How should a parent screen correctly capture data sent back from a route it pushed with Navigator.push?
- a.Use the child route's BuildContext to call setState on the parent after Navigator.pop.
- b.Store the result in a global state object before calling Navigator.pop in the child.
- c.Await the Future returned by Navigator.push, which completes with the Navigator.pop result.Correct
- d.Assign Navigator.push to a variable and read the result synchronously on the next line.
Why? this is the answer
Navigator.push returns a Future that completes with the value passed to Navigator.pop, so awaiting it is the correct pattern. Reading it synchronously fails because the route is still active and the result is not yet available.
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