Why you should implement Code Generators with Xtend.

1. Code Generation with
Sven Efftinge - itemis

2. What is it?

3. Successor to Xpand
Built with

4. Why ?
much faster (as fast as Java)
much better IDE support
generalized set of features
simpler

5. Code Generation Essentials

6. Template Expression
(aka string concatenation)
same syntax as in Xpand
just an expression
greyspace support!

8. static typing
simply Java
no pluggable type system
can be emulated with
active annotations

9. longitude & latitude

15. higher-order functions
map, filter, flatten, etc.
it’s just library!

16. class TypeProviderExample {
def getHourlyData() {
data.weather.hourlys
}
def getTimeWithHighestSwell() {
hourlyData.sortBy[swellheightM].head.time
}
def getAverageWindSpeed() {
hourlyData.map[windspeedkmph].reduce[a,b|a+b] / hourlyData.size
}
}

17. dynamic dispatch

18. dynamic dispatch

19. dynamic dispatch
easily debuggable & extendable

20. dynamic dispatch
def generate(ETypedElement e) {
switch e {
EAttribute : '''
attribute
'''
EReference case e.isContainment: '''
containment reference
'''
EReference : '''
reference
'''
EOperation : '''
operation
'''
default : throw new IllegalArgumentException("not handled : "+e)
}
}
dispatch over type and state
first come
first serve

21. modularization

22. AOP?

23. Dependency Injection!

24. class MainGenerator {
@Inject extension EcoreGen ecoreGenerator
def doGenerate(EClass it) '''
class «name» {
«FOR f : EStructuralFeatures»
«f.generate»
«ENDFOR»
}
'''
}
class EcoreGen {
def dispatch generate(EAttribute attribute) '''
generate attribute
'''
def dispatch generate(EReference reference) '''
generate reference
'''
def dispatch generate(EOperation operation) '''
generate operation
'''
}
declare the dependency

25. class MySpecialEcoreGen extends EcoreGen {
override dispatch generate(EAttribute attribute) '''
special EAttribute
'''
def dispatch generate(EParameter param) '''
parameter
'''
}
class CustomizedGenerator {
def static void main(String[] args) {
val injector = Guice::createInjector [
bind(typeof(EcoreGen)).to(typeof(MySpecialEcoreGen))
]
val mainGenerator = injector.getInstance(typeof(MainGenerator))
mainGenerator.doGenerate(EcorePackage::eINSTANCE.EClass)
}
}
Extend the class you want to modify
Use Guice to wire up the generator

26. content assist
syntax coloring
quick assist outline
rename refactoring
formating
call hierarchy
type hierarchy
extract method
debugging
etc...
IDE Support

27. But why always a DSL?

28. MyBean
String value
class

29. MyBean
String value
class {
}
@Observable

38. future work
tooling via library
more macro support
embedded languages
snappiness!

39. Thank you!
@svenefftinge / @xtext / @xtendlang (c) 2013 by