when<TResult extends Object?> method

@optionalTypeArgs TResult when<TResult extends Object?>(TResult $default(double amount, String currency, String merchantTransactionId, int mid, String paymentMode, String productType, String terminalId, String transactionDate, String? txnNote, String txnType, int udf1, String udf2, String udf3, String udf4, String udf5, String udf6, String udf7, String udf8, String udf9, String udf10, String callbackUrl, String ru,))

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?>(TResult Function( double amount,  String currency,  String merchantTransactionId,  int mid,  String paymentMode,  String productType,  String terminalId,  String transactionDate,  String? txnNote,  String txnType,  int udf1,  String udf2,  String udf3,  String udf4,  String udf5,  String udf6,  String udf7,  String udf8,  String udf9,  String udf10,  String callbackUrl,  String ru)  $default,) {final _that = this;
switch (_that) {
case _PgRequest():
return $default(_that.amount,_that.currency,_that.merchantTransactionId,_that.mid,_that.paymentMode,_that.productType,_that.terminalId,_that.transactionDate,_that.txnNote,_that.txnType,_that.udf1,_that.udf2,_that.udf3,_that.udf4,_that.udf5,_that.udf6,_that.udf7,_that.udf8,_that.udf9,_that.udf10,_that.callbackUrl,_that.ru);case _:
  throw StateError('Unexpected subclass');

}
}