retainWhere method Null safety

void retainWhere (
  1. bool test(
    1. E element
    )
)
override

Removes all objects from this list that fail to satisfy test.

An object o satisfies test if test(o) is true.

List<String> numbers = ['one', 'two', 'three', 'four'];
numbers.retainWhere((item) => item.length == 3);
numbers.join(', '); // 'one, two'

Throws an UnsupportedError if this is a fixed-length list.

Implementation

void retainWhere(bool test(E element)) {
  _filter(test, true);
}