Matthew Weier O'Phinney has posted the second part of his look at decorators in Zend Framework applications. This time he shows the process behind using multiple decorators to alter the same content pushed through each, one after the other.
You may have noticed in the previous installment that the decorator's render() method takes a single argument, $content. This is expected to be a string. render() will then take this string and decide to either replace it, append to it, or prepend it. This allows you to have a chain of decorators -- which allows you to create decorators that render only a subset of the element's metadata, and then layer these decorators to build the full markup for the element.
He gives the example of a custom form element (as was created in the previous part) and how to split it out into two different parts - one object for the main input element and the other to alter the object and add a label. He mentions overcoming a few issues like appending content instead of overwriting, controlling the order they run in and marking where to add the new content to the content of the object.