Processing User Interactions

The View class is responsible for detecting user interactions and raising named events so the Leaf class can process them, make decisions, update the LeafModel, and ultimately refresh the View.

Detecting interactions directly using the WebRequest object

As the View class generates the HTML output it 'knows' about how a browser behaves and so you have freedom to decide how to detect user interaction. View classes can define the 'parseRequest()' function which will be called by the Leaf system and provides your View with an opportunity to detect interactions:

class BlogArticleView extends View
{
    public function parseRequest(WebRequest $request)
    {
        // Detect if the request contains ?helpful=1
        if ($request->get("helpful", false)){
            // Raise an event to the Leaf so it can update the blog
            // article 'helpful' score
            $this->model->voteHelpfulEvent->raise();
        }
    }

    protected function printViewContent()
    {
        ?>
        <!-- Lots of lovely blog related HTML here.... -->
        <p><a href='?helpful=1'>I found this helpful.</a></p>
        <?php
    }
}

Many control components will use this approach to detect changes to their values.

Detecting interactions using nested components

Detecting interactions manually involves repeated plumbing code and can introduce fragility. The module-leaf-common-controls module wrap the standard HTML form inputs into a collection of ready made control components. These components handle the manual detection of interaction for you and raise simple events you can handle.

Because data binding handles events for you from input controls the most common component you need to actually configure for interaction is the Button component. Here is the same example rewritten using a Button component.

class BlogArticleView extends View
{
    protected function createSubLeaves()
    {
        $this->registerSubLeaf(
            new Button("VoteHelpful", "I found this helpful", function(){
                $this->model->voteHelpfulEvent->raise();
            });
    }

    protected function printViewContent()
    {
        ?>
        <!-- Lots of lovely blog related HTML here.... -->
        <p><?=$this->leaves["VoteHelpful"];?></p>
        <?php
    }
}

This approach is the favoured approach if it is possible to build your interface using nested leaf components.