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A Implementation - Resolving Partial Models

In the previous post The Model Factory, I mentioned a couple of methods on the ModelFactory class that can be used to resolve partial models.

But first, what are partial models? The way DD4T publishes linked Components depends on a parameter LinkLevels on the TBB Generate dynamic component. This parameter indicates the number of levels to follow Component Links and to generate additional models for them. Its default value 1 means that only one level of Component Links will be followed starting with the current Component that is being published and this linked Component will only be published as a collection of metadata, while the Fields and MetadataFields collections are empty. These are partial models, because they contain only some information about the Component.

When to use higher values for LinkLevels and when not? If we increase the LinkLevels, the original Component model will contain models for all linked Components. This is very convenient when hopping from one Component to the other, but it creates a few problems:
  • the size of the original model grows exponentially
  • consistency across models is not maintained (same model can be accessed via different routes and one must publish all linking Components in order to keep the linked Component models consistent)
The other option would be to keep LinkLevels value to 1. This means, on the other hand, that in order to load the linked Component model we must:
  • publish it as a Dynamic Component Presentation (with its own dynamic CT)
  • load it on its own using the ComponentFactory and/or ModelFactory
Of course, different situations demand different solutions. I would choose LinkLevel = 1 for content models that are highly linked and where the same Component is linked to via multiple routes. This is also the situation I am presenting in this post regarding the ResolveModel methods in the ModelFactory.

The ResolveModel methods are to be used when we need the whole complete model of the linked Component and what we have initially is only a partial model. The idea is to pass the partial model along with a view name or template TcmUri and the ModelFactory should return a fully created strong typed model.

The ResolveModel methods come in two flavours -- one taking only a model as parameter and resolve it, the other taking an IList of models and resolving each partial model.

    public T ResolveModel<T>(T model, string viewOrTemplateUri) where T : ModelBase
        return GetModel<T>(model.Id, viewOrTemplateUri);

    public IList<T> ResolveModels<T>(IList<T> models, string viewOrTemplateUri) where T : ModelBase
        return models.Select(x => ResolveModel<T>(x, viewOrTemplateUri)).Where(x => x != null).ToList<T>();

The implementations are quite trivial, as seen above, but they make life a lot easier when we need to resolve a single or a collection of partial models:

    IModelFactory modelFactory = DependencyResolver.Current.GetService<IModelFactory>();
    device.Metadata.RelatedAssets = modelFactory.ResolveModels(device.Metadata.RelatedAssets, "Asset");

In the example above we have a collection of partially resolved Asset models linked from the metadata of a Device model.

First, the code calls the ResolveModels method passing in the collection of partially resolved Asset models and a view name.

Next, I replace the collection of partially resolved models on the Device metadata with the collection of fully resolved Asset models.


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