Discussion

When this method is invoked, the rac_delegateProxy will become the receiver’s delegate. Any previous delegate will become the [RACDelegateProxy rac_proxiedDelegate], so that it receives any messages that the proxy doesn’t know how to handle. Setting the receiver’s delegate afterward is considered undefined behavior.

Returns a signal which will send the current text upon subscription, then again whenever the receiver’s text is changed. The signal will complete when the receiver is deallocated.