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Code Structure
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The components of EXT:solrfluid have been developed with the domain driven design (DDD) approach (https://de.wikipedia.org/wiki/Domain-driven_Design) for our extension we tried to separate the code by the following layers:

* **Domain**: Everything that is related to the "search" domain should be implemented here.
* **System**: Everything that is related to the "system" (e.g. TYPO3 specific) should be implemented here.

Domain Layer & Domain Model
===========================

The classes of the domain layer are located in "Classes/Domain" and should contain everything that is related to the "search domain".

ResultSet
---------

The "SearchResultSet" is the main entity that you get passed to the view. It can be used to access all search related objects on your result page.

.. figure:: /Images/Development/uml_resultset.png

    UML diagram of the SearchResutSet

The SearchResultSet can be used e.g. to get facets and spelling suggestions. A focus for the first release was a new domain model for facets,
that can be rendered with fluid or any other template engine.

**Facets**

The following UML diagram shows the implemented facets in EXT:solrfluid. Every facet has one or more facet items attached.
For the **OptionsFacet** the FacetItem is an **Option**, for the **NumericRangeFacet** a **NumericRange**.

Rendering of a facet:

Based on the **"type"** TypoScript configuration the **"FacetRegistry"** chooses the responsible facet package class that
is used to create the object structure from the Solr repsonse. Each facet type is shipped with a default fluid partial, that is able to render such a facet.

A facet package consists of the following parts:

* The facet parser: Responsible to parse the Apache Solr response into a domain object structure
* The url decoder: Responsible to decode the url fragment of the facet in EXT:solr
* The query builder: Responsible to build the needed query fragment for Apache Solr to apply the facet

The TypoScript configuration **"partialName"** can be used to force the rendering with another fluid partial.

For advanced use cases you can use the **"FacetRegistry"** to register your own facet type or overwrite the facet behaviour for a certain facet type.

.. figure:: /Images/Development/uml_facets.png

    UML diagram of the \*Facet classes

As you see in the diagram above Solr ships a clean object structure of the facets, that you can render in your custom templates as you need them.