Difference between Ret and Fwd

Both of these types allow specifying a callback or call-forward, usually to an actor method but possibly to some other destination. But there are some important differences:

• Ret can be called only once, and Fwd may be called many times
• Ret cannot be cloned, but Fwd has ref-counting and there may be many references to the same Fwd callback
• Ret can capture "move" types
• Ret is consumed when it is called
• Ret notifies the callback if it is dropped without being called

Whilst the names suggest uses of returning or forwarding data, there are no restrictions about where the data is sent. So a Ret may 'return' data back to some other actor than the caller if required.