14.1: Why Do We Need Seaside?

Last updated
Save as PDF

Page ID: 39654

\( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \) \( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)\(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\) \(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\)\(\newcommand{\AA}{\unicode[.8,0]{x212B}}\)

Modern web applications try to interact with the user in the same way as desktop applications: they ask the user questions and the user responds, usually by filling in a form or clicking a button. But the web works the other way around: the user’s browser makes a request of the server, and the server responds with a new web page. So web application development frameworks have to cope with a host of problems, chief among them being the management of this inverted control flow. Because of this, many web applications try to forbid the use of the browser’s Back button due to the difficulty of keeping track of the state of a session. Expressing non-trivial control flows across multiple web pages is often cumbersome, and multiple control flows can be difficult or impossible to express.

Seaside is a component-based framework that makes web development easier in several ways. First, control flow can be expressed naturally using message sends. Seaside keeps track of which web page corresponds to which point in the execution of the web application. This means that the browser’s Back button works correctly.

Second, state is managed for you. As the developer, you have the choice of enabling backtracking of state, so that navigation Back in time will undo side-effects. Alternatively, you can use the transaction support built into Seaside to prevent users from undoing permanent side-effects when they use the back button. You do not have to encode state information in the URL — this too is managed automatically for you.

Third, web pages are built up from nested components, each of which can support its own, independent control flow. There are no HTML templates — instead valid HTML is generated programmatically using a simple Smalltalk-based protocol. Seaside supports Cascading Style Sheets (CSS), so content and layout are cleanly separated.

Finally, Seaside provides a convenient web-based development interface, making it easy to develop applications iteratively, debug applications interactively, and recompile and extend applications while the server is running.