when<TResult extends Object?> method

@optionalTypeArgs TResult when<TResult extends Object?>({ required TResult invalidShippingField(InvalidShippingField field, String? message), required TResult unserviceableShippingAddress(String? message), required TResult invalidCouponCode(String? message), required TResult expiredCouponCode(String? message), })

A switch-like method, using callbacks.

As opposed to map, this offers destructuring. It is equivalent to doing:

switch (sealedClass) {
  case Subclass(:final field):
    return ...;
  case Subclass2(:final field2):
    return ...;
}

Implementation

@optionalTypeArgs TResult when<TResult extends Object?>({required TResult Function( InvalidShippingField field,  String? message)  invalidShippingField,required TResult Function( String? message)  unserviceableShippingAddress,required TResult Function( String? message)  invalidCouponCode,required TResult Function( String? message)  expiredCouponCode,}) {final _that = this;
switch (_that) {
case _ApplePaySheetErrorInvalidShipping():
return invalidShippingField(_that.field,_that.message);case _ApplePaySheetErrorUnserviceableShipping():
return unserviceableShippingAddress(_that.message);case _ApplePaySheetErrorInvalidCouponCode():
return invalidCouponCode(_that.message);case _ApplePaySheetErrorExpiredCouponCode():
return expiredCouponCode(_that.message);case _:
  throw StateError('Unexpected subclass');

}
}