join<T1, T2> function

T2? join<T1, T2>(
  1. T2? f(
    1. T1
    ),
  2. T1? x
)

null safe join function null -> null x -> f(x) : T1 ->T2?

Implementation

T2? join<T1, T2>(T2? Function(T1) f, T1? x) => x == null ? null : f(x);