description

# operator [] method Null safety

dynamic operator [] (

1. Object? key

)

Retrieves the zone-value associated with `key`.

If this zone does not contain the value looks up the same key in the parent zone. If the `key` is not found returns `null`.

Any object can be used as key, as long as it has compatible `operator ==` and `hashCode` implementations. By controlling access to the key, a zone can grant or deny access to the zone value.

## Implementation

    dynamic operator [](Object? key);