Drupal 7 Module Development

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Chapter 6
This callback simply gives us an unordered list of all of the artwork types we have
available. Each one is presented as a link to the manage page for that type. Note that
we are converting the artwork type to use dashes instead of underscores in the path.
That is a Drupal standard that we will use as well.
function artwork_type_page_title($type) {
return t('Manage @type', array('@type' => $type->name));
}
We want the title of each page to be a string based on the type that is passed in, so
we need to specify a title callback. The title callback couldn't be simpler:
function artwork_information($artwork_type) {
return $artwork_type->name . ': ' . $artwork_type->description;
}
The summary page for each artwork type is trivial as well, at least in our case.
A more complex entity type would have various configuration options here in a
form, much the way nodes do. In our case, however, we will just show the title
and description of the artwork type.
Believe it or not, that's it. Because we're not allowing any other user configuration
of artwork types ourselves, setting up that minimal skeleton is all we need to do.
However, if the Field UI module is enabled we should see Manage fields and
Manage display tabs when viewing each of those artwork types.
Go to the Painting page, then select Manage fields. Add a new single-line text field
called Artist, just as you would for a node. Now go to Sculpture and add the now
existing Artist field to that artwork type.
That's the biggest advantage of making a new data object an entity. All of the power
of Fields we get for free that way. Take note that even fields that normally attach to
node types are available to us. We can now build up the entire data model of our
artworks without writing any additional code, using all of the Field types available
to us either in core or in contributed modules.
Adding artworks
Now that we have our artwork types hooked up, we need to be able to create
them. Again modeling on the way nodes work let's add the following new entries
to our menu hook:
function artwork_menu() {
$items['artwork/add'] = array(
'title' => 'Add new artwork',
'page callback' => 'artwork_add_page',