A DD4T.net Implementation - Everything's a Label

In my past couple of DD4T implementations, I came to realize that I am making heavy usage of a Label mechanism.

Naturally, I do this in order to internationalize my views. All strings that are not coming from Tridion (as content fields or metadata) and need to appear on the page, must come from a label.

In order to achieve this, I used Rob's excellent approach to Labels In Dynamic Delivery For Tridion, but that's not what I want to blog about here. In short, there are System Components in Tridion that are published as models and contain many key-value pairs representing each label. These Label Components are localized and translated, thus making your website/application internationalized.

But what I want to blog about here is much more than that. Namely, I noticed that besides the models published for Page/Component, DD4T is lacking many of the metadata that is useful for building models, rendering views, or simply getting information about items in Tridion, such as:

• mapping names to TcmUris -- this simple feature would allow access to configuration values in DD4T in a unified way and in a context aware (i.e. Publication aware) situation. Example: being able to refer to a Component Template TcmUri by simply mentioning the View name;
• retrieving arbitrary object metadata -- for example reading Publication metadata fields in DD4T;

To achieve this capability, I came up with a set of templates that are to be placed on the Label Page Template in the Tridion CM. Their goal is to create additional labels -- next to those already explicitly specified by the Label Components on the page -- adding information about mapping between names and TcmUris or Publication metadata.

I devised Template Building Blocks that look for Tridion items inside Publication container that are then used to create labels. I am looking for the following:

• Schemas -- creates mapping labels from RootElement (the label key) to TcmUri of Schema (the label value);
• Component Templates -- maps View Name metadata field to CT TcmUri;
• Categories -- maps XmlName to Category TcmUri;
• Publication metadata -- maps field names to field values;

Since the labels are a very flat structure, a dictionary actually, I need to prefix each of the generated label keys somehow and try make it unique so it doesn't collide with a user-specified label key. For example, for View name mappings I use key "VIEW-" + the name of the view, for Schemas "SCHEMA-" + RootElement names, etc.

In DD4T, I added additional utility methods to Rob's DD4TResourceProvider, which allow retrieval of normal and 'special' labels:

public static string GetLabel(string key)
{
    string publicationUrl = UriHelper.GetPublicationUrl(HttpContext.Current);
    IDictionary resources = GetResourceCache(publicationUrl);
    if (!resources.Contains(key))
    {
        return key;
    }

    return (string)resources[key];
}

public static string GetViewLabel(string viewOrTcmUri)
{
    if (UriHelper.IsValidTcmUri(viewOrTcmUri))
    {
        return viewOrTcmUri;
    }

    string templateUri = GetLabel("VIEW-" + viewOrTcmUri);
    return UriHelper.IsValidTcmUri(templateUri) ? templateUri : viewOrTcmUri;
}

public static string GetTaxonomyLabel(string categoryName)
{
    if (UriHelper.IsValidTcmUri(categoryName))
    {
        return categoryName;
    }

    string taxonomyUri = GetLabel("CATEGORY-" + categoryName);
    return UriHelper.IsValidTcmUri(taxonomyUri) ? taxonomyUri : categoryName;
}

The general idea is that if a label for the requested key is not available, the key itself will be returned.

Moreover, the viewOrTcmUri can be either a view name, and then it will be resolved and the mapped TcmUri will be retrieved (if found), or the viewOrTcmUri representing a TcmUri is returned.

The helper method UriHelper.GetPublicationUrl simply looks at the first one or two directory levels in the current request path and returns that as PublicationUrl identifier.

The other helper method UriHelper.IsValidTcmUri checks whether the parameter matches a RegularExpression identifying a TcmUri pattern.