WAComponent>>inform: to display a simple message for the
user. Here's an example:
renderContentOn: html html anchorWithAction: [self sayHello] text: 'Say hello'.Basically this tells the renderer to create an anchor and execute our block when that anchor is followed. Here's an implementation of
sayHello:
sayHello self inform: 'Hello!'Now play with the application in your web browser. Don't worry about just how
inform: works...its effect is obvious. Note
that when the OK button is pressed our original component
is displayed.
Quite often an anchor's action just changes the state of the
component and returns. That is, it doesn't display anything itself.
There are lots of examples of this in the code included with Seaside.
Look at WACounter, for example. There is already an
excellent tutorial
on WACounter so I'll just show a simple example of
changing a string displayed by our component. At the moment our
component doesn't have any state so lets add a name
instance variable:
WAComponent subclass: #HelloWorldComponent instanceVariableNames: 'name' classVariableNames: '' poolDictionaries: '' category: 'SCSeasideTutorial'Now we give it an initial value and supply some methods to change the value:
initialize super initialize. name := 'Anonymous user' bobIsHere name := 'Bob' janeIsHere name := 'Jane'Now we modify our render method to display the name and allow us to change it:
renderContentOn: html html heading: 'Welcome ' , name level: 1. html anchorWithAction: [self bobIsHere] text: 'Bob'. html br. html anchorWithAction: [self janeIsHere] text: 'Jane'Try this new version of the application. Follow the links and see that the heading changes to reflect the name. Pretty simple huh? Now press the "New Session" link at the bottom of the web browser page. Notice that you get a fresh version of the component (the name is reset to "Anonymous user"). How does Seaside know when to use an existing instance of your root component versus creating a new one? Basically this information is placed in the anchors. Follow one of the anchors and you'll notice that the URL contains a parameter named "_s":
WASession associated with each active
session which can be accessed by evaluating self
session. We will make extensive use of this later. The
renderer takes care of making sure your session ID appears in internal
(callback) anchors and in forms. There are low level methods in the
renderer that generate forms and anchors without the session
information. These methods are useful when you want to link to an
external web site.
anchorWithUrl:text: such as:
renderContentOn: html html anchorWithUrl: 'http://www.amazon.com' do: 'Amazon'Of course the second argument can be any renderable. When a user leaves your site through such an anchor, their association with their session will be lost (unless they use the "back button" to return to your site). Sometimes it is nice to raise a new window when they're leaving your site. Seaside provides some simple javascript code to and convenience methods to support these "popup windows":
renderContentOn: html html anchorWithPopupUrl: 'http://www.amazon.com' extent: 400@350 text: 'Amazon'.If the user's browser doesn't support javascript (or it has been disabled) this will act like a normal anchor.