whenOrNull<TResult extends Object?> method

TResult? whenOrNull<TResult extends Object?>(
  1. TResult? callback(
    1. String isbn13,
    2. DateTime updatedAt
    )?
)

Invoke the original callback when supplied, otherwise return null.

Implementation

TResult? whenOrNull<TResult extends Object?>(
  TResult? Function(String isbn13, DateTime updatedAt)? callback,
) => callback?.call(isbn13, updatedAt);