forEach method Null safety

void forEach(
  1. void f(
    1. String key,
    2. String value
    )
)
override

Applies action to each key/value pair of the map.

Calling action must not add or remove keys from the map.

final planetsByMass = <num, String>{0.81: 'Venus', 1: 'Earth',
  0.11: 'Mars', 17.15: 'Neptune'};

planetsByMass.forEach((key, value) {
  print('$key: $value');
  // 0.81: Venus
  // 1: Earth
  // 0.11: Mars
  // 17.15: Neptune
});

Implementation

void forEach(void f(String key, String value)) {
  for (var i = 0; true; i++) {
    final key = _key(i);
    if (key == null) return;

    f(key, this[key]!);
  }
}