Kotlin: The Next Frontier for Modern (Meta)Programming

With growing complexity in our software systems, technology companies now dedicate greater effort to design product infrastructure to ensure modularity, low-cost solutions, and scalability. Object Oriented Programming (OOP)'s tendency of designing object-models for domain solutions in addition to its merits in handling large data and reducing complexity makes its usage a natural choice in the industry. Despite universal usage, Java's limitations in language techniques fail to capture all domain design decisions in a cohesive manner. This issue describes aspects of relational domains, in which scattering and tangling between mapped sources and targets forces large-scale projects to sacrifice domains that guarantees quality software. Kotlin's open-source community is active, its uses are ever-expanding, and its future is bright. This session intends to analyze a general definition of crosscutting and how it affects growing software, how Aspect-Oriented Programming (AOP) attempts to tackle crosscutting, shortcomings in Java’s current approaches in reflexive programming, and subsequently discuss my experiences with TornadoFX in solving day-to-day business inefficiencies through my first attempt at metaprogramming. Exploration through examples will provide insight in Kotlin’s approaches to metaprogramming intended to expose Kotln's predisposition to AOP. By harnessing the power of Kotlin, we can make strides in creating a foundation for rational framework for metaprogramming.

Transcript

1. Kotlin: The Next Frontier for Modern (Meta) Programming Amanda Hinchman-Dominguez @hinchman_amanda Kotlin, TornadoFX and Metaprogramming
2. Thomas Nield
3. TornadoFX a JavaFX Framework written in Kotlin
4. Characteristics of Functional Languages Functions are treated as first class citizens Functions have no side-effects Metaprogramming capabilities
5. Metaprogramming is magic!! • Programs that treat programs as data – read, analyze, or transform other programs • Metaprogramming can be used to make our lives easier
7. Primitive Filters remove(a, b) && ! or(a, b) )= || ( ( )= topEdge(a) )= shiftUp( == ) !( Piq: cesarloose
8. A READABLE Horizontal Edge
9. A MEMORY-OPTIMAL Horizontal Edge
10. Crosscutting = (Scattering && Tangling) • Scattering – when a source element is related to multiple target elements • Tangling – when a target element is related to multiple source elements • Crosscutting occurs if there exists both scattering & tangling • “spaghetti code” sources targets
11. Metaprogramming A solution to crosscutting • We sacrifice one domain design decision for another • Metaprogramming comes in different forms • Wizards - “Monkey patching” • Aspect-Oriented Programming (AOP) • Domain Specific Languages (DSLs) Flickr: Susan Lucas Hhoffman
14. Aspect-Oriented Programming (AOP) • AOP is how Java approaches crosscutting • Draws out a higher level of abstraction to act as a weaver between concerns Flickr: Chris Radcliffe
15. Memoization - optimization technique
16. Java Annotations API
17. How does Java achieve AOP? 1. Declare the @interface 2. Specify the @Retention and its targets 3. Add elements
18. How does Java achieve AOP? • Dynamic introspection prime for reflection • Runtime annotation carries through to the JVM
19. Current Shortcomings in Aspect-Oriented Programming • Annotations are only a form of metadata • No direct effect on the annotated code • Annotation processing occurs only at designated annotations • No dynamic generation for elements • True metaprogramming doesn’t play nicely with static types • Generating code without compiling risks type-checking • True metaprogramming does not respect encapsulation • Statically-typed languages overcomplicate
20. Imperative v. Declarative Programming Salting your food • An imperative approach (HOW): I see the salt is out of my reach. If I reach over the beans and the sauce and avoiding knocking the drinks over I could probably get it without brushing over my own food. • A declarative approach (WHAT): Pass the salt please. • Execution is more efficient • Reduced bugs Flickr: Joe King
21. Domain-Specific Languages (DSLs) • Regular DSLs • Cares about a specific concern and nothing else • Not a general purpose language & difficult to combine with • Kotlin creates internal DSLs • Uses its own language • Retains key advantages of DSLs
22. Type-Safe CSS • Blocks, or { }, can be passed when the terminal parameter is a function op -> () • Type-safe builders allows Kotlin-based DSLs to create complex hierarchies in a declarative way
23. Higher Order Functions and Lambdas Function as a Parameter
24. Function as a Parameter Parameter types Return type Receiver type Higher Order Functions and Lambdas
25. Parameter types Return type Receiver type Higher Order Functions and Lambdas A.(B) C or (A, B) C Function as a Parameter
26. Reified Generics • Function bytecode copies into every place where the function is called • When the function is called the compiler modifies the generated bytecode to use the corresponding class directly • Can be used • Type checks/casts • Use the Kotlin reflection API • As a type argument to call other functions
27. Scopes • simple constructs used to pass objects like models to other classes • Makes the View/Controller unique to a smaller subset of instances in an application
28. Passing Scopes to Components
29. Type parameter used in receiver and return types Generic-Class-as-a-Parameter Pattern Type parameter declaration – any Component may be passed
30. Passing Scopes with Reified Generics “reified” declares that this type parameter will not be erased at runtime
31. Passing Scopes to Components
32. • Metaprogramming is a solution to crosscutting • Common forms of metaprogramming has their shortcomings • TornadoFX leverages functional Kotlin features to streamline JavaFX The Takeaway
34. TORNADOFX SUITE
35. • True reflection does not respect encapsulation • Generating code at runtime means no compiler for type- checking Challenges w/ Statically-Typed Metaprogramming
37. Special Thanks Carl Walker @bekwaminc Edvin Syse @edvinsyse Thomas Neild @thomasneild9727 Ruckus T Boom @ruckustboom • #TornadoFX channel on Slack • Kotlin community • KotlinConf Committee • Ebad Ahmadzadeh
38. Noted Projects: • TornadoFX - https://github.com/edvin/tornadofx • TilesFX - https://github.com/HanSolo/tilesfx • TornadoFX-DnD-TilesFX – https://github.com/ahinchman1/TornadoFX-DnD-TilesFX • Neighborhood Cat Scheduler – https://github.com/Kotlin- Thursdays/Neighborhood-Cat-Scheduler • TornadoFX-Suite - https://github.com/ahinchman1/TornadoFX-Suite • Kastree - https://github.com/cretz/kastree