Snippet 11: Late and lazy

main.dart

// Here's another pattern that `late` can
// help with: lazy initialization for
// expensive non-nullable fields.
// 
// Try running this code without changing
// it. What do you think will change if
// you make `_cache` a `late` field?

int _computeValue() {
  print('Computing value...');
  return 3;
}

class CachedValueProvider {
  final _cache = _computeValue();
  int get value => _cache;
}

void main() {
  print('Calling constructor...');
  var provider = CachedValueProvider();
  print('Getting value...');
  print('The value is ${provider.value}!');
}

// Fun fact: once you add `late` to the
// declaration of `_cache`, you can move
// the `_computeValue` function into the
// `CachedValueProvider` class and the
// code will still work! Initialization
// expressions for `late` fields can use
// instance methods in their initializers.