Fun with Types - Speaker Deck

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FUN WITH TYPES Created by / Breno Ferreira @breno_ferreira

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IS YOUR CODE EXPLICIT?

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FOR EXAMPLE d e f d i v ( x : I n t , y : I n t ) = x / y

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WHAT HAPPENS WHEN? d i v ( 2 , 0 )

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java.lang.ArithmeticException: / by zero

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HIDDEN SIDE-EFFECTS

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WHAT ABOUT THIS ONE? ( ) = > T

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A SIMPLE GETTER! IT CAN'T GO WRONG!

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Getters are used in Objects. Objects cause Side-Effects!

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FOR EXAMPLE: v a l s j o b s : ( ) = > S t r i n g s j o b s ( ) / / : " A p p l e I " s j o b s ( ) / / : " A p p l e I I " s j o b s ( ) / / : " M a c i n t o s h ! " s j o b s ( ) / / : " ✗"

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SO: ( ) = > T r y [ T ]

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FOR EXAMPLE: v a l s j o b s : ( ) = > S t r i n g s j o b s ( ) / / : " i P h o n e " s j o b s ( ) / / : " i P a d " s j o b s ( ) / / : " i C l o u d " s j o b s ( ) / / : " ✝"

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MAKING EVERYTHING EXPLICIT: ( ) = > T r y [ O p t i o n [ T ] ]

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WHAT ABOUT A GETTER OF GETTERS? ( ) = > ( ) = > T r y [ O p t i o n [ T ] ]

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EXTRACT TO INTERFACE t r a i t I t e r a b l e [ T ] { g e t I t e r a t o r : I t e r a t o r [ T ] } t r a i t I t e r a t o r [ T ] { h a s N e x t : B o o l e a n n e x t : T }

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WHAT IF IT'S ASYNC?

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GETTER ( ) = > T r y [ T ]

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ASYNC GETTER ( ( T r y [ T ] ) = > ( ) ) = > ( )

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BASICALLY, A FUTURE t r a i t F u t u r e [ T ] { o n S u c c e s s : T = > ( ) o n F a i l u r e : E x c e p t i o n = > ( ) }

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WHAT ABOUT MANY ASYNC VALUES?

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EASY: ( ( T r y [ I t e r a b l e [ T ] ] ) = > ( ) ) = > ( )

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BETTER: ( ( T r y [ O p t i o n [ T ] ] ) = > ( ) ) = > ( )

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OBSERVABLE/OBSERVER t r a i t O b s e r v a b l e [ T ] { s u b s c r i b e ( o b s e r v e r : O b s e r v e r [ T ] ) } t r a i t O b s e r v e r [ T ] { o n N e x t ( v a l u e : T ) o n E r r o r ( e r r o r : E x c e p t i o n ) o n C o m p l e t e d ( ) }

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FOUR BASIC EFFECTS IN COMPUTING: One Many Sync T / Option[T] Iterable[T] Async Future[T] Observable[T]