Your very first macro method in Apache Groovy

http://greachconf.com/sessions/your-very-first-macro-method/
https://github.com/bsideup/macro-methods-workshop

Transcript

1. Macro methods Sergei Egorov @bsideup
2. About me DevOps Advocate at ZeroTurnaround Apache Groovy Committer Created MacroGroovy & groovy macro methods
3. About me DevOps Advocate at ZeroTurnaround Apache Groovy Committer Created MacroGroovy & groovy macro methods Got drunk and fell yesterday at speakers’ dinner, lol :D
4. Macro Methods And why should you care?
5. Groovy awesomeness
6. Groovy awesomeness Runtime
 meta-programming
7. Groovy awesomeness Runtime
 meta-programming Compile-time
 meta-programming
8. Groovy awesomeness Runtime
 meta-programming Compile-time
 meta-programming ( ask someone else :D )
9. Groovy awesomeness Runtime
 meta-programming Compile-time
 meta-programming ( ask someone else :D ) Local AST transformations
10. Groovy awesomeness Runtime
 meta-programming Compile-time
 meta-programming ( ask someone else :D ) Local AST transformations Global AST transformations
11. Global AST transformations
12. Ask him!
13. GORM’s GlobalDetachedCriteriaASTTransformation
14. def criteria = new DetachedCriteria(Person).build { eq 'lastName', 'Simpson' } def bartQuery = criteria.build { eq 'firstName', 'Bart' }
15. def criteria = new DetachedCriteria(Person).build { eq 'lastName', 'Simpson' } def bartQuery = criteria.build { eq 'firstName', 'Bart' } Aha! Macro method!!1
16. Groovy’s AstBuilder.buildFromCode
17. def result = new AstBuilder().buildFromCode { while (true) { x++; continue } }
18. def result = new AstBuilder().buildFromCode { while (true) { x++; continue } } Macro method!
19. What’s in common?
20. They’re global AST transformations
21. Scenario 1. Find a method call
22. Scenario 1. Find a method call 2. analyse it
23. Scenario 1. Find a method call 2. analyse it 3. Using its arguments, produce new Expression
24. Scenario 1. Find a method call 2. analyse it 3. Using its arguments, produce new Expression 4. Replace that method call with what we got in #3
25. Smells like demo
26. What can you implement?
27. def fact(num) { return match(num) { String >> fact(num.toInteger()) (0 | 1) >> 1 2 >> 2 _ >> _ * fact(_ - 1) } } Pattern Matching
28. def fact(num) { return match(num) { String >> fact(num.toInteger()) (0 | 1) >> 1 2 >> 2 _ >> _ * fact(_ - 1) } } Pattern Matching Scala? ewww!
30. def fact(num) { return match(num) { when String then fact(num.toInteger()) when 0 or 1 then 1 when 2 then 2 orElse it * fact(it - 1) } } DSL-like Pattern Matching
31. doWithData { assert a + b == c where: a | b || c 1 | 2 || 3 4 | 5 || 9 7 | 8 || 15 } Spock-like data tables
32. // your awesome library here ?