My brief talk about my attempt to build an internal version of the WebDSL language.

1. Internal DSLs
in Scala
Zef Hemel
Medewerker no. 0855447

2. Java++

3. header("Add entry")
form {
table {
row {
col { text("Your name:") }
col { newEntry.name = input(newEntry.name) }
}
row {
col { text("Your message:") }
col { newEntry.text = inputText(newEntry.text) }
}
}
button("Post") {
newEntry.save()
goto(Home())
}
}

4. in Scala

5. Pages

6. case class Home() extends Page {
def ui {
header("Welcome to my guestbook!")
section {
header("All entries")
list {
for (e <- cache("entries", Entry.all)) {
listitem {
form {
text(e.name)
text(": ")
text(e.text)
button("Delete") {
e.delete()
goto(Home())
}
}
}
}
}
}
}
}

7. Templates

8. case class Home() extends Page {
def ui {
header("Welcome to my guestbook!")
section {
entries
}
}
def entries {
header("All entries")
list {
for (e <- cache("entries", Entry.all)) {
listitem {
form {
text(e.name)
text(": ")
text(e.text)
button("Delete") {
e.delete()
goto(Home())
}
}
}
}
}
}
}

9. abstract class MainTemplate extends Page {
def body
def ui {
block("headerblock") {
header {
navigate(Home()) {text("My Guestbook")}
}
}
hr
body
hr
text("(C) 2009, Zef Hemel")
}
}

10. case class Home() extends MainTemplate {
def body {
header("Welcome to my guestbook!")
section {
entries
}
}
def entries {
header("All entries")
for (e <- cache("entries", Entry.all)) {
listitem {
form {
text(e.name)
text(": ")
text(e.text)
button("Delete") {
e.delete()
goto(Home())
}
}
}
}
}
...
}

11. Styling

12. object DefaultStyle extends Style {
block("headerblock") >> header {
fontsize = 30 pt;
width = 100 percent;
bgcolor = "#eeeeee";
}
section >> header {
color = "#0c0ccc";
}
body {
fontfamily = "Helvetica, Arial, Verdana, sans-serif"
}
}

13. abstract class MainTemplate extends Page {
def body
style = DefaultStyle
def ui {
block("headerblock") {
header {
navigate(Home()) {text("My Guestbook")}
}
}
hr
body
hr
text("(C) 2009, Zef Hemel")
}
}

14. Access Control
(added this morning in 15 lines of code)

15. case class CannotEnter() extends Page with AccessControl {
def canAccess = false
def ui {
text("You should never see this!")
}
}

16. Data model

17. class Entry extends DataObject {
def singleton = Entry
@Column var name : String = ""
@Column var text : String = ""
}
object Entry extends DataObjectSingleton(classOf[Entry])

18. How?

19. OO features
basic: classes, objects, inheritance, reflection
traits

20. function
programming
closures

21. flexible syntax
a >> b == a.>>(b)
form { ... } ~= form(() => { ... })

22. implicits
8 pt == new UnitIntWrapper(8).pt
Entry.all == Entry.all(dbSession)

23. type inference
var newEntry = Entry()
==
var newEntry : Entry = Entry()

24. Advantages

25. “languages” as libraries
trivial “language” composition

26. Limitations

27. Scala → JVM

28. model checking
==
type checking

29. boiler plate
case class Home() extends Page {
def ui {
}
}