Introduction

David Shaffer

Why Seaside?

Maybe more accurately "What attracted me to Seaside?". If you're not comfortable with anecdotal motivations or you've never used any other web programming frameworks, skip this section. I've been working with web development frameworks for years. I've used everything from Python CGI scripts, to PHP and Java Server Pages. I've used scaffolding built on top of these technologies as well as built some of my own. Many of these technologies, such as WebOjects® and Java Server Faces, gave me hints of what web development could be like but they all fell short in one area or another. In most cases the component model was weak. In others the flow of the application was encumbered with transporting data along with it (ever had to sneak data into hidden fields or anchors simply to "move" it from one form to another?). Such encumberances limit reuse of components. Seaside attracted me because is has

a solid component model with decorators and callbacks,
support for sequencing interactions, and
native (Smalltalk) debugging interface.

None of these features is impossibly difficult to envision implementing but anyone who has set to implement frameworks with these characteristics knows that there are many decisions and compromises to make along the way. These decisions give the framework its unique flavor. Here are some of the decisions that the Seaside developers made:

all session state is maintained on the server,
HTML is generated completely in Smalltalk, no templates or "server pages" (although it isn't hard to build such things in Seaside),
encourage the use of CSS to customize application appearence
use callbacks for anchors and buttons, rather than loosely coupled page references,
use native language (Smalltalk) support for continuations to implement sequencing,
others?

Combined these features make working with Seaside much like writing a GUI application. Actually, in some ways simpler, since the web browser takes a lot of the application details out of your hands. Using continuations means the state in your application is localized to the scope on which it is relevant. No need to store temporary variables in the session (or hidden fields or anchors) just to move them between pages. No need to build URL's from session data or configuration files to properly control the flow of your complex applications. If you've used other frameworks then Seaside's somewhat unique characteristics will likely attract you as they did me.

Seaside Limitations

Many of the decisions discussed in the previous section present limitations to the developer. Here are some:

Seaside applications are memory intensive, requiring about 100Kb-10Mb per session
"Web page developers" (or graphics artists) will have to learn CSS!
Seaside is not particularly performant although you can design your applications to scale well with the addition of new servers

As Seaside is becoming more widely used I hope to give more concrete examples of performance-related problems and solutions. This tutorial shows you how to deploy applications to a small group of concurrent users (around 50 concurrent users, 2-3 requests per second peak on a low end server). As people push the envelope I hope to have more to say on the topic.

Prerequisite: Smalltalk

I will assume that you can find your way around the Squeak Smalltalk environment so that I don't have to go into too much detail. If you are completely new to Smalltalk or Squeak you can still work your way through this tutorial as long as you are determined to do so. In fact, it is a great way to learn Smalltalk...total immersion. Still you will need supplemental materials to help you learn the language and the development environment. If you fit in this category take a short break now and collect a few sources of information:

Find a free Smalltalk book that suites your learning style or look on amazon for print copies.
Bookmark a few web sites with helpful information including:
- The Squeak Swiki
- The Seaside web site
Subscribe to the squeak-dev and seaside mailling lists and find out how to search the archives.
Find a newsgroup or two (comp.lang.smalltalk is great!)

Great. Now you have enough tools at your disposal to help you through any problems you might encounter. The Smalltalk-related mailling lists that I use (VWNC, squeak-dev and the Seaside mailling list) are chock full of helpful and friendly people. Do your reading but if you're still stuck don't hesitate to post a question.

Organization of this document

This document has two sections each divided into units. The first section forms an introduction to Seaside. This material moves slowly through the Seaside framework in a bottom up fashion and is appropriate for programmers with no Seaside experience. The second section is divided into more topical units. The flow of these units is less clear than the introductory text. You might find yourself skipping around in the section, reading only topics which are of interest to you. You should cover the first unit, "Building Applications", since it brings together the introductory topics and talk about how you should structure Seaside applications.

This document looks best when viewed in a 1024x768 window using 16pt or smaller fonts. Much of the sample code requires 16pt or smaller monospaced font.

Introduction

Why Seaside?

Seaside Limitations

Prerequisite: Smalltalk

Organization of this document

Other tutorials