Page History

...

With Tapestry's If component you can only test one condition at a time. In order to distinguish multiple cases, you'd have to write complex nested if/else constructs in your page template and have a checker method for each test inside your page class. Wiki Markup{float:right|background=#eee|padding=0 1em} *JumpStart Demo:* [If, Not, Negate, Switch, Else, Unless|http://jumpstart.doublenegative.com.au/jumpstart/examples/lang/ifnotnegateswitchelseunless] {float}

In cases where you have to distinguish multiple cases, the Delegate component comes in. It delegates rendering to some other component, for example a Block. For each case you have, you basically wrap the content inside a Block that doesn't get rendered by default. You then place a Delegate component on your page and point it to a method inside your page class that will decide which of your Blocks should be rendered.

...