description

# retainWhere abstract method

void retainWhere(

1. bool test(
   1. E value
   )

)

Removes all elements of this set that fail to satisfy `test`.

    final characters = <String>{'A', 'B', 'C'};
    characters.retainWhere(
        (element) => element.startsWith('B') || element.startsWith('C'));
    print(characters); // {B, C}

## Implementation

    void retainWhere(bool test(E element));