# Class List The classes and protocols in Google Tag Manager for Mobile Apps SDK for iOS:

|---|---|
| [TAGContainer](https://developers.google.com/tag-platform/tag-manager/ios/v3/reference/interface_t_a_g_container) | A class that provides access to container values |
| [\<TAGContainerCallback\>](https://developers.google.com/tag-platform/tag-manager/ios/v3/reference/protocol_t_a_g_container_callback-p) | A protocol that a client may implement to receive information when the contents of the container has been successfully loaded or failed to load |
| [\<TAGContainerFuture\>](https://developers.google.com/tag-platform/tag-manager/ios/v3/reference/protocol_t_a_g_container_future-p) | A class that implements this protocol waits for the container to be available and provides access to the container |
| [TAGContainerOpener](https://developers.google.com/tag-platform/tag-manager/ios/v3/reference/interface_t_a_g_container_opener) | A helper class for opening containers |
| [\<TAGContainerOpenerNotifier\>](https://developers.google.com/tag-platform/tag-manager/ios/v3/reference/protocol_t_a_g_container_opener_notifier-p) | A class that implements this protocol will receive a notification when a container is available for use |
| [TAGDataLayer](https://developers.google.com/tag-platform/tag-manager/ios/v3/reference/interface_t_a_g_data_layer) | The data layer is a dictionary holding generic information about the application |
| [\<TAGFunctionCallMacroHandler\>](https://developers.google.com/tag-platform/tag-manager/ios/v3/reference/protocol_t_a_g_function_call_macro_handler-p) | A protocol implemented by the application to calculate the value of a function call macro |
| [\<TAGFunctionCallTagHandler\>](https://developers.google.com/tag-platform/tag-manager/ios/v3/reference/protocol_t_a_g_function_call_tag_handler-p) | A protocol implemented by the application to execute a custom tag |
| [\<TAGLogger\>](https://developers.google.com/tag-platform/tag-manager/ios/v3/reference/protocol_t_a_g_logger-p) | A protocol for error/warning/info/debug/verbose logging |
| [TAGManager](https://developers.google.com/tag-platform/tag-manager/ios/v3/reference/interface_t_a_g_manager) | A class that is the mobile implementation of Google Tag Manager (GTM) |