firstNonNull function

dynamic firstNonNull (
  1. dynamic o1,
  2. dynamic o2,
  3. [dynamic o3,
  4. dynamic o4]
)

Returns the first non-null argument.

If all arguments are null, throws an ArgumentError.

Users of Dart SDK 2.1 or later should prefer:

var value = o1 ?? o2 ?? o3 ?? o4;
ArgumentError.checkNotNull(value);

If o1 is an Optional, this can be accomplished with o1.or(o2).

Implementation

dynamic firstNonNull(o1, o2, [o3, o4]) {
  // TODO(cbracken): make this generic.
  if (o1 != null) return o1;
  if (o2 != null) return o2;
  if (o3 != null) return o3;
  if (o4 != null) return o4;
  throw ArgumentError('All arguments were null');
}