Write Android like Scala

Presentation in http://roppongi-aar.connpass.com/event/21907/
Write Android like Scala.
Introduction of my library Android-Monad.
Enjoy Android programming with Monadic data types!
https://github.com/petitviolet/Android-Monad

Transcript

1. Write Android
   like Scala
   @petitviolet
   Fringe81 Co,. Ltd.
   
   

   View Slide

2. About me
   • Hiroki Komurasaki
   • @petitviolet
   • Fringe81 Co., Ltd.
   • Scala: Ad server
   • Android (iOS): Ad SDK
   
   

   View Slide

3. What is the pain
   of Android?
   
   

   View Slide

4. 
   

   View Slide

5. 
   

   View Slide

6. 
   ON
   NOT
   

   View Slide

7. 
   Nice point of Scala
   • first class function
   • `Awesome` data structures
   • Option, List, Either, Future, Try, …
   

   View Slide

8. 
   Nice point of Scala
   • first class function
   • `Awesome` data structures
   • Option, List, Either, Future, Try, …
   • Functional Programming
   • Monad
   

   View Slide

9. Monad is
   • `flatMap` in Scala
   • `>>=` in Haskell
   • “すごいH本”
   
   

   View Slide

10. petitviolet/Android-Monad
    
    

    View Slide

11. Maybe
    
    

    View Slide

12. 
    

    View Slide

13. 
    

    Maybe itemId = Maybe.of(x);
    // Maybe findItemById(int id);
    itemId.flatMap(this::findItemById)

    .map(Item::getCost)
    .map(integer -> integer + 5)

    .filter(integer -> integer % 2 == 0)

    .foreach(integer -> {

    Log.d(TAG, "result: " + integer);

    });
    Maybe
    

    View Slide

14. 
    

    Maybe itemId = Maybe.of(x);
    // Maybe findItemById(int id);
    itemId.flatMap(this::findItemById)

    .map(Item::getCost)
    .map(integer -> integer + 5)

    .filter(integer -> integer % 2 == 0)

    .foreach(integer -> {

    Log.d(TAG, "result: " + integer);

    });
    Maybe
    

    View Slide

15. 
    

    Maybe itemId = Maybe.of(x);
    // Maybe findItemById(int id);
    itemId.flatMap(this::findItemById)

    .map(Item::getCost)
    .map(integer -> integer + 5)

    .filter(integer -> integer % 2 == 0)

    .foreach(integer -> {

    Log.d(TAG, "result: " + integer);

    });
    Maybe
    

    View Slide

16. 
    maybeInt.flatMap(new Function.F1>() {

    @Override

    public Maybe invoke(Integer integer) {

    return findItemById(integer);

    }

    }).map(new Function.F1() {

    @Override

    public Integer invoke(Item item) {

    return item.getCost();

    }

    }).map(new Function.F1() {

    @Override

    public Integer invoke(Integer integer) {

    return integer + 5;

    }

    }).filter(new Function.F1() {

    @Override

    public Boolean invoke(Integer integer) {

    return integer % 2 == 0;

    }

    }).foreach(new Function.F() {

    @Override

    public void invoke(Integer integer) {

    Log.d(TAG, "result: " + integer);

    }

    });
    

    View Slide

17. Maybe
    • Null safe programming in Java
    • if (foo != null)
    • Maybe Monad
    • of, flatMap
    • Useful APIs
    • map, getOrElse, foreach, filter, …
    
    

    View Slide

18. 
    ListM categoryIds = ListM.of(1, 2, 3);
    ListM findItemsByCId(int id);
    int sumCost = categoryIds
    .flatMap(this::findItemsByCId)

    .filter(item -> item.getStatus() == 1)

    .map(Item::getCost)

    .foldLeft(0, (acc, i) -> acc + i);
    ListM
    

    View Slide

19. 
    ListM categoryIds = ListM.of(1, 2, 3);
    ListM findItemsByCId(int id);
    int sumCost = categoryIds
    .flatMap(this::findItemsByCId)

    .filter(item -> item.getStatus() == 1)

    .map(Item::getCost)

    .foldLeft(0, (acc, i) -> acc + i);
    ListM
    

    View Slide

20. 
    ListM categoryIds = ListM.of(1, 2, 3);
    ListM findItemsByCId(int id);
    int sumCost = categoryIds
    .flatMap(this::findItemsByCId)

    .filter(item -> item.getStatus() == 1)

    .map(Item::getCost)

    .foldLeft(0, (acc, i) -> acc + i);
    ListM
    

    View Slide

21. 
    ListM someViewListM = ListM.of(…);
    int sumOfInput = someViewListM

    .map(l -> ((EditText) l.findViewById(R.id.input)))

    .map(editText -> editText.getText().toString())

    .filterNot(s -> TextUtils.isEmpty(s))

    .map(Integer::parseInt)

    .foldLeft(0, (acc, i) -> acc + i);
    ListM
    

    View Slide

22. 
    ListM someViewListM = ListM.of(…);
    int sumOfInput = someViewListM

    .map(l -> ((EditText) l.findViewById(R.id.input)))

    .map(editText -> editText.getText().toString())

    .filterNot(s -> TextUtils.isEmpty(s))

    .map(Integer::parseInt)

    .foldLeft(0, (acc, i) -> acc + i);
    ListM
    

    View Slide

23. 
    ListM someViewListM = ListM.of(…);
    int sumOfInput = someViewListM

    .map(l -> ((EditText) l.findViewById(R.id.input)))

    .map(editText -> editText.getText().toString())

    .filterNot(s -> TextUtils.isEmpty(s))

    .map(Integer::parseInt)

    .foldLeft(0, (acc, i) -> acc + i);
    ListM
    

    View Slide

24. 
    

    View Slide

25. ListM
    • List Monad
    • of, unit, flatMap
    • for(int i = 0; i <= list.size(); i++) { // }
    • Useful Collection APIs
    • map, foreach, filter, filterNot, partition
    • foldLeft, foldRight, bindMaybe
    
    

    View Slide

26. Android-Monad(0.5.0)
    • Maybe
    • ListM
    • State
    • Identity
    
    

    View Slide

27. We are hiring!
    fringe81.com/recruit
    

    View Slide