description

# update method Null safety

V update (

1. K key,
2. V update(
   1. V value
   ),
3. {V ifAbsent(
   )}

)
override

Updates the value for the provided `key`.

Returns the new value of the key.

If the key is present, invokes `update` with the current value and stores the new value in the map.

If the key is not present and `ifAbsent` is provided, calls `ifAbsent` and adds the key with the returned value to the map.

It's an error if the key is not present and `ifAbsent` is not provided.

## Implementation

    V update(K key, V update(V value), {V Function()? ifAbsent}) =>
        _map.update(key, update, ifAbsent: ifAbsent);