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class MyScaffold extends StatelessWidget {
  var restClient = RestClient();
  var dropDownCurrencies = DropDownCurrency();

  @override
  Widget build(BuildContext context) {
    // Material is a conceptual piece of paper on which the UI appears.

    restClient.loadConfig().then((value) {
      print("load finish. result: ${value.status}");
      if (value.status == Status.failure) {
        print("error: ${value.message}");
      } else {
        print(
            "data: currencies size: ${(value.data as Config).currencyList
                .length}, merchant size: ${(value.data as Config).merchantList
                .length}");
        setUpViewForConfig((value.data as Config).currencies);
      }
    });

    return Scaffold(
      // Column is a vertical, linear layout.
      body: Column(
        children: <Widget>[
          AppBar(
            title: Text('Oats Dumb Terminal'),
          ),
          //....
          dropDownCurrencies,
          //...
        ],
      ),
    );
  }

  void setUpViewForConfig(List<Currency> currencies) {
    dropDownCurrencies.setCurrencyItems(currencies); //how it make?
  }
}


class DropCurrency extends StatefulWidget {
  @override
  State<StatefulWidget> createState() => DropDownState()
}

class DropDownState extends State<DropCurrency> {
  List<String> currencyList = List();

  void setCurrencyItems(List<Currency> currencyList) {
    setState(() {
      this.currencyList = currencyList.map((curr) {
        return curr.currencyName;
      }).toList();
    });
  }

  @override
  Widget build(BuildContext context) {
    return SizedBox(
        width: double.infinity,
        child: Container(
            alignment: Alignment.centerLeft,
            padding: EdgeInsets.only(left: 8.0),
            child: Column(
              crossAxisAlignment: CrossAxisAlignment.start,
              children: <Widget>[
                Text(
                  'Select Currency',
                  textAlign: TextAlign.left,
                ),
                currencyList.isEmpty
                    ? Text('loading...')
                    : DropdownButton<String>(
                  items: currencyList.map((String curr) {
                    return DropdownMenuItem<String>(
                      value: curr,
                      child: Text(curr),
                    );
                  }).toList(),
                  hint: Text('Currencies...'),
                  onChanged: (_) {},
                )
              ],
            )));
  }
}