Tuesday, October 20, 2009

Link with confirmation


This is  a component that adds confirmation to a regular EventLink. It does this by using the TapestryExt.js library introduced in my previous post to trigger a link after intercepting and cancelling it first. It works both with and without zones.

It is used excactly like an EventLink, with an additional “message” parameter, to display in confirmation box.

For now, I only implemented a standard javascript confirm box. But it shouldn’t be too hard extending this with more fancy interaction with DHTML.

I’m not completely comfortable with the techniques used here. Some of it looks a lot like a hack in my opinion, especially the part about intercepting/cancelling a zone listener and re-adding it afterwards using copy-paste from tapestry.js.


 * Displays a javascript confirmation box before actually triggering the link.
 * @author Inge
@IncludeJavaScriptLibrary({"TapestryExt.js, "ConfirmLink.js"})
public class ConfirmLink implements ClientElement {    
  private RenderSupport renderSupport;  
  @Parameter("literal:Do you really want to delete?")
  private String message;
  @Component(publishParameters="event,zone,context", inheritInformalParameters=true)
  private EventLink confirmLink;
  void afterRender() {
    String url = confirmLink.getLink().toRedirectURI();
    renderSupport.addScript("new ConfirmLink('%s', '%s', '%s')", confirmLink.getClientId(), url, message);
  public String getClientId() {
    return confirmLink.getClientId();



var ConfirmLink = Class.create({
  initialize: function(element, url, message) {
    this.element = $(element);
    this.url = url;
    this.message = message;
    this.initListeners = this.initListeners.bind(this);
    // Makes it run after Tapestry:init to be able to delete
    // zone listener added by Tapestry and start listening for
    // our modded version instead.    
  onclick: function(event) {
    if (confirm(this.message)) {
      TapestryExt.triggerLink(this.element, this.url);
  initListeners: function() {
    this.element.stopObserving('click'); // Remove zone update, will be re-added later by TapestryExt.js.
    this.element.observe('click', this.onclick.bindAsEventListener(this));

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