StreamMapper (Ratpack API (2.0.0-rc-1))

Type Parameters:

U - the type of item emitted from upstream

D - the type of item to emit downstream (i.e. post transform)
```
public interface StreamMapper<U,D>
```
Fundamentally transforms a stream.

Since:

1.4

See Also:

Streams.streamMap(Publisher, StreamMapper)

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`WriteStream<U>`	`map(Subscription subscription, WriteStream<D> downstream)`	A transform step in a `Publisher` chain.

- Method Detail
  - map
```
WriteStream<U> map(Subscription subscription,
                   WriteStream<D> downstream)
            throws Exception
```
    A transform step in a Publisher chain.
    
    Parameters:
    
    subscription - the upstream subscription
    
    downstream - the downstream to write to
    
    Returns:
    
    a write stream that receives signals from upstream
    
    Throws:
    
    Exception - any error in establishing the mapping