In this presentation, I show how to build an Xtext based DSL for iPhone and Android aplications.

1. Building DSLs with Eclipse
Peter Friese, itemis
@peterfriese
@xtext
www.itemis.de
(c) 2009 Peter Friese. Distributed under the EDL V1.0 - http://www.eclipse.org/org/documents/edl-v10.php
More info: http://www.peterfriese.de / http://www.itemis.com

2. Think about your job!

3. Feel like this?

4. Because

5. Because
you need to write

6. Because
you need to write
lots of boring code?

7. Wrong Level of Abstraction!
http://www.flickr.com/photos/rykerstribe/3222969466/

8. DSL
o p a
m e n
a c g
i i u
n f a
i g
c e

9. DSL
A language...
...that lets you express your intention
... that solves one problem
... that doesn’t get in your way
... that fits your situation
... that’s formal and processable
... that’s simple and easy to learn

14. Some DSLs
you might have
heard of

15. select name, salary
from employees
where salary > 2000
order by salary

16. <project name="MyProject" default="dist" basedir=".">
<property name="src" location="src"/>
<property name="build" location="build"/>
<property name="dist" location="dist"/>
<target name="init">
<mkdir dir="${build}"/>
</target>
<target name="compile" depends="init">
<javac srcdir="${src}" destdir="${build}"/>
</target>
<target name="dist" depends="compile">
<mkdir dir="${dist}/lib"/>
<jar jarfile="${dist}/lib/MyProject.jar"
basedir="${build}"/>
</target>
<target name="clean">
<delete dir="${build}"/>
<delete dir="${dist}"/>
</target>
</project>

17. <project name="MyProject" default="dist" basedir=".">
<property name="src" location="src"/>
<property name="build" location="build"/>
<property name="dist" location="dist"/>
<target name="init">
<mkdir dir="${build}"/>
</target>
<target name="compile" depends="init">
<javac srcdir="${src}" destdir="${build}"/>
</target>
<target name="dist" depends="compile">
<mkdir dir="${dist}/lib"/>
<jar jarfile="${dist}/lib/MyProject.jar"
basedir="${build}"/>
</target>
<target name="clean">
<delete dir="${build}"/>
<delete dir="${dist}"/>
</target>
</project>

18. External
or
Internal

19. Internal DSLs

20. Mailer.mail()
.to(“you@gmail.com”)
.from(“me@gmail.com”)
.subject(“Writing DSLs in Java”)
.body(“...”)
.send();

21. Simple

22. Limited

23. External DSLs

25. 1)Create ANTLR grammar
2)Generate lexer / parser
3)Parser will create parse tree
4)Transform parse tree to semantic model
5)Iterate model
6)Pass model element(s) to template

26. Lack of symbolic integration
Writing parsers / generators is complicated
IDE support is inferior / non-existent

27. Flexible

28. Adaptable

29. Complicated

30. Why not use a DSL...
... for building DSLs?

31. http://www.eclipse.org/Xtext/
@xtext

32. ar
Model
m
m
ra
G
Generator
Runtime
Superclass
Subclass Class
LL(*) Parser ECore meta model Editor

33. ar
Model
m
m
ra
G
Generator
Runtime
Superclass
Subclass Class
LL(*) Parser ECore meta model Editor

34. Grammar (similar to EBNF)
grammar org.xtext.example.Entity with org.eclipse.xtext.common.Terminals
generate entity "http://www.xtext.org/example/Entity"
Model:
(types+=Type)*;
Type:
TypeDef | Entity;
TypeDef:
"typedef" name=ID ("mapsto" mappedType=JAVAID)?;
JAVAID:
name=ID("." ID)*;
Entity:
"entity" name=ID ("extends" superEntity=[Entity])?
"{"
(attributes+=Attribute)*
"}";
Attribute:
type=[Type] (many?="*")? name=ID;

35. grammar org.xtext.example.Entity
with org.eclipse.xtext.common.Terminals Meta model inference
generate entity
"http://www.xtext.org/example/Entity"
entity Rules -> Classes
Model:
(types+=Type)*;
Model
Type:
TypeDef | Entity;
types
TypeDef: *
Type
"typedef" name=ID
name: EString
("mapsto" mappedType=JAVAID)?;
superEntity
JAVAID:
name=ID("." ID)*; TypeDef Entity
Entity: mappedType attributes
"entity" name=ID
Attribute
("extends" superEntity=[Entity])? JAVAID
name: EString
"{" name: EString
many: EBoolean
(attributes+=Attribute)*
"}"; type
Attribute:
type=[Type] (many?="*")? name=ID;

36. grammar org.xtext.example.Entity
with org.eclipse.xtext.common.Terminals Meta model inference
generate entity
"http://www.xtext.org/example/Entity"
entity Alternatives -> Hierarchy
Model:
(types+=Type)*;
Model
Type:
TypeDef | Entity;
types
TypeDef: *
Type
"typedef" name=ID
name: EString
("mapsto" mappedType=JAVAID)?;
superEntity
JAVAID:
name=ID("." ID)*; TypeDef Entity
Entity: mappedType attributes
"entity" name=ID
Attribute
("extends" superEntity=[Entity])? JAVAID
name: EString
"{" name: EString
many: EBoolean
(attributes+=Attribute)*
"}"; type
Attribute:
type=[Type] (many?="*")? name=ID;

37. grammar org.xtext.example.Entity
with org.eclipse.xtext.common.Terminals Meta model inference
generate entity
"http://www.xtext.org/example/Entity"
entity Assignment -> Feature
Model:
(types+=Type)*;
Model
Type:
TypeDef | Entity;
types
TypeDef: *
Type
"typedef" name=ID
name: EString
("mapsto" mappedType=JAVAID)?;
superEntity
JAVAID:
name=ID("." ID)*; TypeDef Entity
Entity: mappedType attributes
"entity" name=ID
Attribute
("extends" superEntity=[Entity])? JAVAID
name: EString
"{" name: EString
many: EBoolean
(attributes+=Attribute)*
"}"; type
Attribute:
type=[Type] (many?="*")? name=ID;

38. Let’s build a DSL
for Mobile Apps

40. Building DSLs
1. Analyze problem domain
2. Map concepts of problem domain to language
3. (Optional: write interpreter)
4. (Optional: write generator)

41. Analyzing the problem domain
http://www.flickr.com/photos/minifig/3174009125/

42. Anatomy of an iPhone app
View title
Speaker
Table view
Name
Image
Title
Session
Table cell
Location
Tab bar
Entity
Tab bar button
Data Provider

43. Mapping concepts
tabbarApplication jazoonApp {
button {
Entity title= "Schedule"
icon= "83-calendar.png"
Data Provider view= ScheduleList( AllSessions() )
}
button {
Tab bar title= "Speakers"
icon= "112-group.png"
Tab bar button view= SpeakerList( AllSpeakers() )
}
Table view button {
title= "Topics"
View title icon= "44-shoebox.png"
view= TopicList( AllTopics() )
Table cell }
}

44. Mapping concepts
entity Speaker {
String speakerId
String name
Entity
String bio
String organization
String country
Data Provider String smallImageURL
String largeImageURL
Tab bar
}
Session[] talks
Tab bar button entity Session {
String talkId
String title
Table view String abstract
String ^type
View title
String location
String startTime
String endTime
Table cell Speaker[] speakers
Topic[] topics
}
entity Topic {
String topicId
String themeId
String name
}

45. Mapping concepts
Entity contentprovider AllSessions
returns Session[]
Data Provider fetches XML
from "http://jipa.netcetera.ch/talks.xml"
Tab bar selects "feed.entry"
Tab bar button contentprovider AllSpeakers
returns Speaker[]
fetches XML
Table view from "http://jipa.netcetera.ch/speakers.xml"
selects "feed.entry"
View title
Table cell

46. Mapping concepts
contentprovider AllSessions
returns Session[]
fetches XML
Entity from "http://query.yahooapis.com/v1/public/
yql?q=use%20%22http%3A%2F%2FHeikoBehrens.net
Data Provider %2Fjazoon%2Ftalks.xml%22%20as%20talks%3B%0Aselect
%20*%20from%20talks%20where%20omitDetails
Tab bar %3D1&debug=true"
selects "query.results.talks.talk"
Tab bar button contentprovider SessionsByTopic(String id)
returns Session[]
Table view fetches XML
from ("http://query.yahooapis.com/v1/public/
View title yql?q=use%20%22http%3A%2F%2FHeikoBehrens.net
%2Fjazoon%2Ftalks.xml%22%20as%20s%3B%0Aselect%20*
Table cell %20from%20s%20where%20topicId%20%3D
%20%22"id"%22&diagnostics=true&debug=true&debug=true
")
selects "query.results.talks.talk"

47. Mapping concepts
Entity
Data Provider tableview ScheduleList(Session[] sessions) {
title= "Schedule"
Tab bar section {
cell Subtitle foreach sessions as session {
Tab bar button text= session.title
details= session.startTime
action= SessionDetails(
Table view SessionById(session.talkId))
}
View title }
}
Table cell

48. Demo 1

50. Mapping concepts to code

51. «Xpand»

52. Protected regions
Debugger Editor
Outlets
Profiler
Cartridges
Polymorphism
Type safe
Produces any Can run standalone
kind of text Eclipse-based (ANT / Maven)

53. Mapping concepts to code

54. Mapping concepts to code
tableview SpeakerList(
Speaker[] speakers)
{
title= "Speakers"
section
{
cell Default foreach
speakers as speaker
{
text= speaker.name
image= speaker.smallImageURL
action= SpeakerDetails
(SpeakerById(
speaker.speakerId))
}
}
}

55. Mapping concepts to code
tableview SpeakerList( «DEFINE viewModule FOR
Speaker[] speakers) SectionedView»
{ «FILE filenameModule()»
title= "Speakers" #import "«filenameHeader()»"
section #import "NSObject+Applause.h"
{ «EXPAND imports»
cell Default foreach
speakers as speaker @implementation «className()»
{
text= speaker.name «EXPAND sectionCount»
image= speaker.smallImageURL «EXPAND sectionTitleHeader»
action= SpeakerDetails «EXPAND rowCounts»
(SpeakerById( «EXPAND cellDescriptions»
speaker.speakerId)) «EXPAND cellSelections»
} «EXPAND staticData»
} @end
} «ENDFILE»
«ENDDEFINE»

56. Demo 2

57. 3 things to take home

58. 3 things to take home
1 Implementing DSLs is easy with Xtext
2 Xtext delivers great IDE support
3 Symbolic integration is possible

59. More Info?
Xtext Webinar:
http://live.eclipse.org/node/886
www.xtext.org
Consulting:
http://www.itemis.com
@peterfriese | http://peterfriese.de