If you use Ruby on Rails, Django, Perl Catalyst, PHP, or some other popular web framework, but -have programmed in haskell and would like to use the world's greatest language for your next web project, -just keep reading. I promise by the time you're done you will give you all the knowledge you need.
- -This tutorial is its own demo, and it is open source. -We will build a job board, which you can try out for yourself by -creating a user on this demo site, and play with locally after you have installed the source code. -The text you are reading this moment is bundled up too, hence "self-demoing tutorial." -For best results, you should -install and run -it in a local environment where you have control. Then, when you are done -learning, you can use the tutorial code as a starting point for your own -HAppS applications. -
hunk ./templates/home.st 1 -Haskell is a great way to program.
!$ +You also get all the goodness -that comes from programming in haskell, my favorite language.
-!$ - -HAppS is especially great if you believe, like I do, that as -modern software systems tend toward ever increasing complexity, -database usage is an unnecessary source of complication that -should be factored out where possible. - -
Ruby's rails and python's django have become popular largely because of their object relational mapping systems, -which hide the complexity of database engines by converting application data manipulation logic into sql. -When I first used an ORM, it felt like a huge improvement over writing sql statements every time I wanted to manipulate -an application's state. But pretty soon ORMs started seeming hackish to me too. At some point, -the metaphors I wanted to use just broke down. - - -$!Or to put it another way, that sql -is an ugly hack. !$ -
HAppS is haskell's answer to rails and django (and perl's catalyst, - and php). - $! , and every ORM ever written in the history of software) !$ - With HAppS, there is no wrangling data - structures into and out of the database, because there is no database. You use whatever data - structures are natural to your application, and serialize them - transparently using - powerful - machinery that's running behind the - scenes. And if there are existing databases that you need to connect to, you can do that too - -- you're not locked in to using macid for everything. - -
MACID, -the HAppS storage mechanism, is no vanilla serialization layer that will -start acting in weird ways when an application has many concurrent users doing possibly conflicting things. -By leveraging haskell's type system -(see composable memory transactions paper), -you get the same ACID guarantees that -normally only come with a database.
- - -There are some limitations to using macid - as a datastore that you should familiarize yourself with - if you are looking into using HAppS for heavy-usage transactional applications. - But long term, HAppS with macid looks promising enough that I've started - using it as a platform for building commercial web 2.0 type apps. (My first - commercial happs app will be public soon, so stay tuned on - techcrunch. :) ) - -
In short, HAppS is awesome, and webmonkeys everywhere should use it. Except... - -
There is this one minor detail. - +
If you use Ruby on Rails, Django, Perl Catalyst, PHP, or some other popular web framework, but +have programmed in haskell and would like to use the world's greatest language for your next web project, +just keep reading. I promise by the time you're done you will posess all the knowledge +and sample code you need.
hunk ./templates/home.st 13 +This tutorial is its own demo, and it is open source. The tutorial explains how to build a toy job board, which you can try out for yourself by +creating a user on this demo site, and play with locally after you have installed the source code. +The text you are reading this moment is bundled up too, hence "self-demoing tutorial." +For best results, you should +install and run +it in a local environment where you have control. Then, when you are done +learning, you can use the tutorial code as a starting point for your own +HAppS applications. +
hunk ./templates/home.st 23 + hunk ./templates/missinghappsdocumentation.st 3 -Unfortunately, the documentation for HAppS is +
When I started building this demo/tutorial, the documentation for HAppS was hunk ./templates/missinghappsdocumentation.st 5 -So bad that honestly I wouldn't know where to start to fix it. +So bad that honestly I wasn't sure where to start with trying to fix it. hunk ./templates/missinghappsdocumentation.st 11 -that included clear step-by-step instructions for getting from zero to final product. I figure what the HAppS +that included clear step-by-step instructions for getting from zero to final product. +There is still a lot of work to be done in the documentation and usability department. +That haddock still needs to be written, and more than anything, HAppS needs to be used and discussed +by more people in forums, blogs, wikis, and real applications like hackage +(which I think is already using HAppS or will be soon). +These things tend to snowball. My hope is that this tutorial will play a part in bringing +commercial-use HAppS and haskell into the real world. + +
+I figured what the HAppS hunk ./templates/missinghappsdocumentation.st 22 -doing real work by leveraging this technology. So the demo project is a job board. +doing real work by leveraging this technology. + +
In this spirit, the demo project is a job board. hunk ./templates/missinghappsdocumentation.st 27 -$! -Somewhat to my shame, I still haven't learned how HAppS data migrations work, -so every time I release a new version of the tutorial I lose all data -- however, if any real seeming jobs -get posted, I will make sure this doesn't happen. A good explanation of HAppS data migration is my top priority -for the next version anyway. !$ - - -$! There is a real job board, based on code from this tutorial, at fpjobs.com. !$ - -
-By the way, -I am currently available for haskell, HAppS, and startup consulting. -
hunk ./templates/missinghappsdocumentation.st 36 -$! -I created this project, the Real -World HAppS Tutorial, to popularize the use of haskell, with HAppS, in web applications. -!$ - ++On this note, I am currently available for haskell, HAppS, and startup consulting: thomashartman1 at gmail. +Write me if there is anything you need. +
hunk ./templates/missinghappsdocumentation.st 41 - + hunk ./templates/runtutoriallocally.st 8 -The cabal installation may take up to an hour, mainly because the -HAppS-Server installation is slow, but it should succeed in one -shot. This is a symptom of the HAppS slow linking bug. +
The cabal installation is kind of slow. I've had it take up to 15 minutes. But it should succeed in one +shot. (This is a symptom of the HAppS slow linking bug.) + +
Unfortunately, the above statement is false on ghc 6.10.1 at the moment, because
+
the crypto package won't cabal install out of the box. You can build crypto first by doing
+
darcs get http://code.haskell.org/crypto
+
cd crypto
+
cabal install
+
Hopefully the crypto package will get a version bump on hackage soon so I can delete this ugly orange paragraph.
hunk ./templates/runtutoriallocally.st 21
-
As far as I know, this issue does not occur when you run the tutorial from a compiled executable, which is of course + how you should be running for a production application. + hunk ./templates/toc.st 1 -[("/tutorial/home","happs intro") +[("/tutorial/home","build a web 2.0 app in happs") + , ("/tutorial/why-happs-is-cool","why happs is cool")