[Tapestry Wiki] Update of "Tapestry5HowToGetAnHTMLStringFromARenderCommandParameter" by uklance

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The "Tapestry5HowToGetAnHTMLStringFromARenderCommandParameter" page has been changed by uklance:
http://wiki.apache.org/tapestry/Tapestry5HowToGetAnHTMLStringFromARenderCommandParameter

New page:
Sometimes, you may want to specify a parameter in tapestry's markup language (TML) and instead of rendering the HTML directly to the response, you may wish to use it for some other purpose (eg use it in a javascript).

The following is an example of a component dose the following:
 * Accepts a count parameter and a [[http://tapestry.apache.org/tapestry5/apidocs/org/apache/tapestry5/runtime/RenderCommand.html|RenderCommand]] parameter
 * Adds a wrapper div to the markup writer
 * Loops through each count and updates a the "current" property which may be referenced in the RenderCommand parameter
 * Renders the RenderCommand for each iteration through the loop
 * Uses @AfterRender to get the resultant HTML from the wrapper div
 * Removes the wrapper div from the markup so that it is not rendered to the response directly

Page.tml
{{{
<t:tmlToString t:count="5" t:id="tmlToString">
        <p:renderMe>
                <div>foo ${tmlToString.current} bar</div>
        </p:renderMe>
</t:tmlToString> 
}}}

Page.java
{{{
@InjectComponent
@Property
private TmlToString tmlToString; 
}}}

TmlToString.java
{{{
public class TmlToString {
   @Parameter
   @Property
   private RenderCommand renderMe;

   @Property
   @Parameter(defaultPrefix=BindingConstants.LITERAL, required=true)
   private int count;

   @Property
   private int current;

   @Inject
   private JavaScriptSupport javaScriptSupport;

   private Element wrappingDiv;

   @BeginRender
   RenderCommand beginRender() {
      return new RenderCommand() {
         public void render(MarkupWriter writer, RenderQueue queue) {
            wrappingDiv = writer.element("div");
            List<RenderCommand> commands = new ArrayList<RenderCommand>();
            for (int i = 0; i < count; ++ i) {
               final int finalI = i;
               commands.add(new RenderCommand() {
                  public void render(MarkupWriter writer2, RenderQueue queue2) {
                     current = finalI;
                     queue2.push(renderMe);
                  }
               });
            }
            Collections.reverse(commands); // render commands are pushed to the front of the queue
            for (RenderCommand command : commands) {
               queue.push(command);
            }
         }
      };
   }

   @AfterRender
   void afterRender(MarkupWriter writer) {
      writer.end();
      String html = wrappingDiv.getChildMarkup();
      wrappingDiv.remove();
      javaScriptSupport.addScript("alert('%s')", html);
   }
}
}}}

Result
{{{
alert('<div>foo 0 bar</div><div>foo 1 bar</div><div>foo 2 bar</div><div>foo 3 bar</div><div>foo 4 bar</div>');
}}}

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