Checking Supported Features

New features are always being added to SDL, however, you or your users may be connecting to modules that do not support the newest features. If your SDL app attempts to use an unsupported feature your request will be ignored by the module.

When you are implementing a feature you should always assume that some modules your users connect to will not support the feature or that the user may have disabled permissions for this feature on their head unit. The best way to deal with unsupported features is to check if the feature is available before attempting to use it and to handle error responses.

Checking the System Capability Manager

The easiest way to check if a feature is supported is to query the library's System Capability Manager. For more details on how get this information, please see the Adaptive Interface Capabilities guide.

Handling RPC Error Responses

When you are trying to use a feature, you can watch for an error response to the RPC request you sent to the module. If the response contains an error, you may be able to check the result enum to determine if the feature is disabled. If the response that comes back is of the type GenericResponse, the module doesn't understand your request.

// sdl_javascript_suite v1.1+
async function send () {
    const response = await sdlManager.sendRpcResolve(alert);
    if (!response.getSuccess()) {
        // The request was not successful. Check the response's result code for more information
        return;
    }
    // The request was successful
}
send().catch(err => {
    // thrown exceptions will be caught here
    // catch exceptional behavior in a parent function instead of at the RPC sending level
});

// Pre sdl_javascript_suite v1.1
(async function () {
    const response = await sdlManager.sendRpc(request);
    if (!response.getSuccess()) {
        // The request was not successful. Check the response's result code or catch and log the Promise error for more information
        return;
    }
    // The request was successful
})();

Checking if a Feature is Supported by Version

When you connect successfully to a head unit, SDL will automatically negotiate the maximum SDL RPC version supported by both the module and your SDL SDK. If the feature you want to support was added in a version less than or equal to the version returned by the head unit, then your head unit may support the feature. Remember that the module may still disable the feature, or the user may still have disabled permissions for the feature in some cases. It's best to check if the feature is supported through the System Capability Manager first, but you may also check the negotiated version to know if the head unit was built before the feature was designed.

Throughout these guides you may see headers that contain text like "RPC 6.0+". That means that if the negotiated version is 6.0 or greater, then SDL supports the feature but the above caveats may still apply.

const rpcSpecVersion = sdlManager.getRegisterAppInterfaceResponse().getSdlMsgVersion();