Hoover cord bike lock

You know how the power cord for hoovers is on a springloaded coil, such that it is retracted into the body of the box when it is not needed. Wouldn't that be good for cable bike locks? The coil container could be firmly attached to the bike. The cord is extended from the container round a lamppost (or some such) and then locked to the container (the lock is built in). This way, you wouldn't need to worry about carrying the lock around with you (only the key or code) as it's already part of the bike.