1. happs intro
2. the missing happs documentation
3. getting started with happs
4. prerequisites
5. cabal install me
6. main
7. url handling
8. templates
9. stringtemplate basics
10. debugging
11. form data: get and post
12. form data: file uploads
13. cookies
14. introduction to macid
15. using macid safely
16. macid dummy data
17. macid updates and queries
18. changing the data model
19. macid stress test
20. limitations of macid
21. foreign characters
22. cron jobs
23. thanks
24. appendix (floundering in ghci)

StringTemplate Basics

In the previous section we rendered a template in ghci using the following command

*Main Misc View Text.StringTemplate> do templates <- directoryGroup "templates" ; writeFile "output.html" ( renderTemplateGroup templates [] "templates-dont-repeat-yourself" )

Let's look more carefully at these functions.

• The directoryGroup function reads in all *.st type files in a directory, and returns an IO STGroup value, which is basically a group of StringTemplates.
  *Main Misc View Text.StringTemplate> :t (directoryGroup :: String -> IO (STGroup String))
  The actual type of directoryGroup is a little less concrete than the above, and uses type classes.
  Our :t command gives directoryGroup a concrete type, and since there's no error, we know it typechecks.
• renderTemplateGroup takes an STGroup, some template key/value pairs, and a named template, and renders the template if it is found in the STGroup. If it is not found, an error is returned.
  *Main Misc View Text.StringTemplate> :t renderTemplateGroup
  renderTemplateGroup :: STGroup String -> [(String, String)] -> String -> String

Next, let's look at a slightly more involved example of StringTemplate usage than we've seen so far.

• The controller: myFavoriteAnimal, in src/ControllerBasic.hs
  a snip:
    renderTemplateGroup templates
      [("favoriteAnimal", "Tyrannasaurus Rex") , ("leastFavoriteAnimal","Bambi")] $ "myFavoriteAnimalBase"
• The rendered page: my favorite animal
• The template: templates/myFavoriteAnimalBase.st
• A template included from inside an included templates: leastFavoriteAnimal()

Try to gain an understanding of the most important features in the StringTemplate system by getting a sense of how the my-favorite-animal page got generated.

When you're done doing that, you should have enough StringTemplate knowledge to shoot yourself in the foot :)

For a more in depth look at StringTemplate, see the following:

• stringtemplate.org
• HStringTemplate, a haskell port of StringTemplate on hackage
• fmapfixreturn, Sterling Clover's blog

And now, on to macid.