button toggle camera during capturesession

[jojo]

I want to toggle the camera during a capturesession
when a button is pressed
until now i have the following code
but the debugger tells it cannot find the method
Has anyone an idea to do the toggle for a "preview"

- (BOOL) toggleCamera
{
    BOOL success = NO;
    
    if ([self cameraCount] > 1) {
        NSError *error;
        AVCaptureDeviceInput *captureInput;
        AVCaptureDevicePosition position = [[videoInput device] position];
        
        if (position == AVCaptureDevicePositionBack)
            captureInput = [[AVCaptureDeviceInput alloc] initWithDevice:[self frontFacingCamera] error:&error];
        else if (position == AVCaptureDevicePositionFront)
            captureInput = [[AVCaptureDeviceInput alloc] initWithDevice:[self backFacingCamera] error:&error];
        
        else
            goto bail;
        
        AVCaptureSession *captureSession = [[AVCaptureSession alloc] init];
        if (captureInput != nil) {
            
            [captureSession addInput:captureInput];
            
            
            
            AVCaptureVideoDataOutput* captureOutput = [[AVCaptureVideoDataOutput alloc] init];
            [captureOutput setSampleBufferDelegate:self queue:dispatch_get_current_queue()];
            [captureSession addOutput:captureOutput];
            [captureSession startRunning];
            
                    }
    }

    
bail:
    return success;
}