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
   

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2. About me
   DevOps Advocate at ZeroTurnaround
   Apache Groovy Committer
   Created MacroGroovy & groovy macro methods
   

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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
   

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4. Macro Methods
   And why should you care?
   

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5. Groovy awesomeness
   

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6. Groovy awesomeness
   Runtime

   meta-programming
   

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7. Groovy awesomeness
   Runtime

   meta-programming
   Compile-time

   meta-programming
   

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8. Groovy awesomeness
   Runtime

   meta-programming
   Compile-time

   meta-programming
   ( ask someone else :D )
   

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9. Groovy awesomeness
   Runtime

   meta-programming
   Compile-time

   meta-programming
   ( ask someone else :D ) Local AST
   transformations
   

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10. Groovy awesomeness
    Runtime

    meta-programming
    Compile-time

    meta-programming
    ( ask someone else :D ) Local AST
    transformations
    Global AST
    transformations
    

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11. Global AST
    transformations
    

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12. Ask him!
    

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13. GORM’s
    GlobalDetachedCriteriaASTTransformation
    

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14. def criteria = new DetachedCriteria(Person).build {
    eq 'lastName', 'Simpson'
    }
    def bartQuery = criteria.build {
    eq 'firstName', 'Bart'
    }
    

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15. def criteria = new DetachedCriteria(Person).build {
    eq 'lastName', 'Simpson'
    }
    def bartQuery = criteria.build {
    eq 'firstName', 'Bart'
    }
    Aha! Macro method!!1
    

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16. Groovy’s
    AstBuilder.buildFromCode
    

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17. def result = new AstBuilder().buildFromCode {
    while (true) {
    x++;
    continue
    }
    }
    

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18. def result = new AstBuilder().buildFromCode {
    while (true) {
    x++;
    continue
    }
    }
    Macro method!
    

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19. What’s in common?
    

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20. They’re global AST
    transformations
    

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21. Scenario
    1. Find a method call
    

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22. Scenario
    1. Find a method call
    2. analyse it
    

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23. Scenario
    1. Find a method call
    2. analyse it
    3. Using its arguments, produce new Expression
    

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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
    

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25. Smells like demo
    

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26. What can you implement?
    

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27. def fact(num) {
    return match(num) {
    String >> fact(num.toInteger())
    (0 | 1) >> 1
    2 >> 2
    _ >> _ * fact(_ - 1)
    }
    }
    Pattern Matching
    

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28. def fact(num) {
    return match(num) {
    String >> fact(num.toInteger())
    (0 | 1) >> 1
    2 >> 2
    _ >> _ * fact(_ - 1)
    }
    }
    Pattern Matching
    Scala? ewww!
    

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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
    

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31. doWithData {
    assert a + b == c
    where:
    a | b || c
    1 | 2 || 3
    4 | 5 || 9
    7 | 8 || 15
    }
    Spock-like data tables
    

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32. // your awesome library here
    ?
    

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