--- ## Refresh customer token --- This method refreshes the customer’s current token.
Returns an error if the token has expired and cannot be refreshed.
**Declared In:** lib/modules/client/client_impl.dart **Class:** [ClientImpl](/developers/mobile-sdk/class-reference/flutter/modules#client)
**Declaration:** 
Future<void> refreshToken({required void Function() onSuccess, required void Function(SyneriseError) onError}) async
**Parameters:** | Parameter | Type | Mandatory | Default | Description | | --- | --- | --- | --- | --- | | **onSuccess** | Function() | yes | - | Function to be executed when the operation is completed successfully | | **onError** | Function([SyneriseError](/developers/mobile-sdk/class-reference/flutter/miscellaneous#syneriseerror) error) | yes | - | Function to be executed when the operation is completed with an error | **Return Value:** No value is returned. **Example:** 
await Synerise.client.refreshToken(onSuccess: () {
  //onSuccess handling
}, onError: (SyneriseError error) {
  //onError handling
});
**Declaration:** 
Future<bool> refreshToken() async
**Return Value:** **true** if the operation is success, otherwise it throws an error. **Example:** 
await  Synerise.client.refreshToken().catchError((error)
## Retrieve customer token --- This method retrieves the customer’s current, active token.
Returns an error if the token has expired and cannot be retrieved.
**Declared In:** lib/modules/client/client_impl.dart **Related To:** [Token](/developers/mobile-sdk/class-reference/flutter/client#token) **Class:** [ClientImpl](/developers/mobile-sdk/class-reference/flutter/modules#client)
**Declaration:** 
Future<void> retrieveToken({required void Function(Token) onSuccess, required void Function(SyneriseError) onError}) async
**Parameters:** | Parameter | Type | Mandatory | Description | | --- | --- | --- | --- | | **onSuccess** | Function([Token](/developers/mobile-sdk/class-reference/flutter/client#token) token) | yes | - | Function to be executed when the operation is completed successfully | | **onError** | Function([SyneriseError](/developers/mobile-sdk/class-reference/flutter/miscellaneous#syneriseerror) error) | yes | - | Function to be executed when the operation is completed with an error | **Return Value:** No value is returned. **Example:** 
await Synerise.client.retrieveToken(onSuccess: (Token token) {
  //onSuccess handling
}, onError: (SyneriseError error) {
  //onError handling
});
**Declaration:** 
Future<Token> retrieveToken() async
**Return Value:** [Token](/developers/mobile-sdk/class-reference/flutter/client#token) **Example:** 
Token token = await  Synerise.client.retrieveToken().catchError((error)
## Get current customer UUID --- This method retrieves the customer’s current UUID. **Declared In:** lib/modules/client/client_impl.dart **Class:** [ClientImpl](/developers/mobile-sdk/class-reference/flutter/modules#client)
**Declaration:** 
Future<String> getUUID() async
**Return Value:** String **Example:** 
await Synerise.client
        .getUUID()
        .then((result) => {
        //result handling
        });
**Declaration:** 
Future<String> getUUID() async
**Return Value:** String **Example:** 
String uuid = await  Synerise.client.getUUID().catchError((error)
## Regenerate customer --- This method regenerates the UUID and clears the authentication token, login session, custom email, and custom identifier. This operation works only if the customer is anonymous. This operation clears the authentication token, login (if applicable), custom email, and custom identifier. | | **iOS SDK** | **Android SDK** | **React Native SDK** | **Flutter SDK** | | --- | --- | --- | --- | --- | | Introduced in: | 3.3.10 | 3.3.5 | 0.9.0 | 0.7.0 | **Declared In:** lib/modules/client/client_impl.dart **Class:** [ClientImpl](/developers/mobile-sdk/class-reference/flutter/modules#client) **Declaration:** 
Future<void> regenerateUUID() async
**Return Value:** No value is returned. **Example:** 
await Synerise.client
        .regenerateUUID()
        .then((result) => {
        //result handling
        });
## Regenerate customer with identifier --- This method regenerates the UUID and clears the authentication token, login session, custom email, and custom identifier. This operation works only if the customer is anonymous. This operation clears the authentication token, login (if applicable), custom email, and custom identifier The optional `clientIdentifier` parameter is a seed for UUID generation. | | **iOS SDK** | **Android SDK** | **React Native SDK** | **Flutter SDK** | | --- | --- | --- | --- | --- | | Introduced in: | 3.6.5 | 3.6.4 | 0.9.10 | 0.7.2 | **Declared In:** lib/modules/client/client_impl.dart **Class:** [ClientImpl](/developers/mobile-sdk/class-reference/flutter/modules#client) **Declaration:** 
Future<void> regenerateUUIDWithClientIdentifier(String clientIdentifier) async
**Parameters:** | Parameter | Type | Mandatory | Description | | --- | --- | --- | --- | | **clientIdentifier** | String | no | Seed for UUID generation |
The **clientIdentifier** parameter is used for decreasing the number of UUID refreshes, so it must be unique for every customer.
**Return Value:** No value is returned. **Example:** 
await Synerise.client
        .regenerateUUIDWithClientIdentifier(clientIdentifier)
        .then((result) => {
        //result handling
        });
## Destroy current session --- This method destroys the session completely. This method clears all session data (both client and anonymous) and removes cached data. Then, it regenerates the UUID and creates the new anonymous session. **Declared In:** lib/modules/client/client_impl.dart **Class:** [ClientImpl](/developers/mobile-sdk/class-reference/flutter/modules#client)
**Declaration:** 
Future<void> destroySession({required void Function() onSuccess, required void Function(SyneriseError) onError}) async
**Parameters:** | Parameter | Type | Mandatory | Default | Description | | --- | --- | --- | --- | --- | | **onSuccess** | Function() | yes | - | Function to be executed when the operation is completed successfully | | **onError** | Function([SyneriseError](/developers/mobile-sdk/class-reference/flutter/miscellaneous#syneriseerror) error) | yes | - | Function to be executed when the operation is completed with an error | **Return Value:** No value is returned. **Example:** 
await Synerise.client.destroySession(onSuccess: () {
  //onSuccess handling
}, onError: (SyneriseError error) {
  //onError handling
});
**Declaration:** 
Future<void> destroySession() async
**Return Value:** No value is returned. **Example:** 
await  Synerise.client.destroySession().catchError((error)