Preview Mode
============

A preview step can be enabled for an admin entity by overriding the public property 
$supportsPreviewMode and setting it to true.

This will show a new button during create/edit mode named preview.

While in preview mode two buttons will be shown to approve or decline persistance of the
entity. Decline will send you back to the edit mode with all your changes unpersisted but
still in the form so no data is lost and the entity can be further adjusted.
Accepting the preview will store the entity as if the preview step was never there.

Preview can be used to render how the object would look like in your front-end environment.
However by default it uses a template similar to the one of the show action and works with 
the fields configured to be shown in the show view.

Overridding the preview template (SonataAdminBundle:CRUD:preview.html.twig) can be done either
globally through the template configuration for the key 'preview' or per admin entity by
overridding the getTemplate($name) and returning the appropriate template when the key 
matches 'preview'.

.. code-block:: php

    <?php // MyAdmin.php

    public function getTemplate($name)
    {
        switch ($name) {
            case 'preview':
                return 'AcmeDemoBundle:CRUD:preview.html.twig';
                break;
            default:
                return parent::getTemplate($name);
                break;
        }
    }

In either way the template should be extending your own layout, injecting the form in it
and finally overriding the action buttons to show the approve/decline buttons like the 
default preview.html.twig.

The entity is passed to the view in a variable called object. If your original view expects
a different object you can just set your own variables prior to calling parent().

Keep in mind that the whole edit form will now appear in your view. 
Hidding the fieldset tags with css (display:none) will be enough to only show the buttons 
(which still have to be styled according to your wishes) and create a nice preview-workflow.

.. code-block:: jinja

    {% extends 'AcmeDemoBundle::layout.html.twig' %}

    {% use 'SonataAdminBundle:CRUD:base_edit_form.html.twig' with form as parentForm %}

    {% block templateContent %}
        {% set article = object %}
    
        {{ parent() }}
    
        {{ block('parentForm') }}
    {% endblock %}

    {% block formactions %}
        <input class="btn btn-success" type="submit" name="btn_preview_approve" value="{% trans from 'SonataAdminBundle' %}btn_preview_approve{% endtrans %}"/>
        <input class="btn btn-danger" type="submit" name="btn_preview_decline" value="{% trans from 'SonataAdminBundle' %}btn_preview_decline{% endtrans %}"/>
    {% endblock %}