Rx optional support for for react-native-contacts

contacts.js

var ReactNative = require('react-native')
var Contacts = ReactNative.NativeModules.Contacts;

try {
  var Rx = require('rx');

  if (Rx !== 'undefined') {
    function _execAddressBookMethodWithParamsErrorData(func) {
      return Rx.Observable.create(function(observer) {
        func(function(error, data) {
          if (error) {
            observer.onError(error);
          } else {
            observer.onNext(data);
            observer.onCompleted();
          }
        });

        return null;
      });
    }

    function _execAddressBookMethodWithParamError(contact, func) {
      return Rx.Observable.create(function(observer) {
        func(contact, function(error) {
          if (error) {
            observer.onError(error);
          } else {
            observer.onCompleted();
          }
        });

        return null;
      });
    }

    Contacts.rx_checkPermission = function() {
    return _execAddressBookMethodWithParamsErrorData(Contacts.checkPermission);
    };

    Contacts.rx_requestPermission = function() {
      return _execAddressBookMethodWithParamsErrorData(Contacts.requestPermission);
    };

    Contacts.rx_getAll = function() {
      return _execAddressBookMethodWithParamsErrorData(Contacts.getAll);
    };

    Contacts.rx_addContact = function(contact) {
      return _execAddressBookMethodWithParamError(contact, Contacts.addContact);
    }

    Contacts.rx_updateContact = function(contact) {
      return _execAddressBookMethodWithParamError(contact, Contacts.updateContact);
    }

    Contacts.rx_deleteContact = function(contact) {
      return _execAddressBookMethodWithParamError(contact, Contacts.deleteContact);
    }
  }
} catch (ex) {
}

module.exports = Contacts;