Look up the value of key
, or add a new value if it isn't there.
Returns the value associated to key
, if there is one. Otherwise calls ifAbsent
to get a new value, associates key
to that value, and then returns the new value.
Map<String, int> scores = {'Bob': 36}; for (var key in ['Bob', 'Rohan', 'Sophena']) { scores.putIfAbsent(key, () => key.length); } scores['Bob']; // 36 scores['Rohan']; // 5 scores['Sophena']; // 7
Calling ifAbsent
must not add or remove keys from the map.
V putIfAbsent(K key, V ifAbsent()) { if (containsKey(key)) { return this[key]; } return this[key] = ifAbsent(); }
© 2012 the Dart project authors
Licensed under the Creative Commons Attribution-ShareAlike License v4.0.
https://api.dartlang.org/stable/2.0.0/dart-collection/MapMixin/putIfAbsent.html