Firebase path problems

Hey there, Could someone please help me?
I am working on one app where I need to scan QR code.
As known the QR code is just a string.
And the question is can I implement the String QR code read to the Firebase path, so as with the scanning I would get directly to needed database?

At fist I thought simply add it to path like


and then I just got an error from the Xcode, that it waits only for string type data.