Either<L, R>.fromPredicate constructor Null safety

Either<L, R>.fromPredicate(
  1. R r,
  2. bool predicate(
    1. R r
    ),
  3. L onFalse(
    1. R r
    )
)

If calling predicate with r returns true, then return Right(r). Otherwise return Left containing the result of onFalse.

Implementation

factory Either.fromPredicate(
        R r, bool Function(R r) predicate, L Function(R r) onFalse) =>
    predicate(r) ? Either.of(r) : Either.left(onFalse(r));