1. Reactive Android Development
CS T & CS T
Summer 2016
Sodium FRP

2. Observer pattern Very common in GUIs
onClick
More generally, can be applied to data structures
Define an interface to deliver changes
Override accessor methods to deliver changes

3. What could go wrong?

4. What could go wrong?
A -> B
B -> C
C -> A

5. What else could go wrong?

6. What else could go wrong?
A -> B
A -> C
C -> D
B -> D

7. What else else could go wrong?

8. What else else could go wrong?
Code ends up distributed

9. How does Sodium try to fix this
Cells provide the 'listener' behavior automatically

10. How does Sodium try to fix this
Cells provide the 'listener' behavior automatically
Guaranteed update order
Diamond dependencies are not a problem

11. How does Sodium try to fix this
Cells provide the 'listener' behavior automatically
Guaranteed update order
Diamond dependencies are not a problem
Arguably nice tools for working with reactive values

12. Reactive values Cells Streams Hold a value at all time
Can register to be notified of changes
Streams
Represent a stream of ephemeral events
Can register to be notified of events

13. Map Works for cells and streams
Creates a new cell/stream that is the result of applying a function to the input stream
C.map((c)->2*c)

14. Lift
C = A + B

15. Lift
C = A + B
A.lift(B,(a,b) -> a + b);

16. Snapshot
Cell C
Stream E
E.snapshot(C,(e,c) -> f (e,c))

17. Merge
Combines the events of two streams into a single stream.

18. Example Code
GitHub
kbaldor
SodiumTest