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Creating a Computed Field for a Referenced Item

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Developer System Administrator

A Sitecore field can refer to a Sitecore item, which itself contains several fields of its own. Sometimes, you may need to display the fields that are only part of the referenced item in a search interface. This way, you end up with complementary information for each one of your search results. This can be easily done by using what’s called a computed field.

Requirements

  • You have a running instance of the Jetstream Demo (version 2.0) and you generated a few flights using the Generate Flights feature.

    Although this tutorial is based on Jetstream, you can easily adapt the provided code to your specific situation. The underlying principle stays exactly the same.

Putting It Into Context

Jetstream contains items of type Flight (located under sitecore/Content/Global/Flights). A Flight is composed of the following fields.

Field name Field type Example value
Flight Number Single-Line Text 3836
Departure Airport Droptree (reference) Airports/2/3/8/2/0/Amsterdam Airport Schiphol (raw value is actually {23820EE7-87A3-4265-B785-2A1D25C98F72}).
Departure Time Datetime 5/23/2014 10:01 PM
Arrival Airport Droptree (reference) Airports/9/C/2/F/4/Los Angeles International Airport (raw value is actually {9C2F4988-0951-443C-9526-5DBB5D8D9C02}).
Arrival Time Datetime 5/24/2014 12:16 AM
Price Single-Line Text 586

If you choose to display raw field values (under View > Raw Values), you will discover that the Departure and Arrival Airport fields actually contain IDs or GUIDs. This is because they point to items of type Airport (located under sitecore/Content/Global/Airports).

An Airport is composed of the following fields.

Field name Field type Example value
Airport Name Single-Line Text Amsterdam Airport Schiphol
Airport Code Single-Line Text AMS
City Single-Line Text Amsterdam
State Single-Line Text  
Country Single-Line Text Netherlands
Time Zone Droplink (+1:00) Central Europe Standard Time
Latitude Number 52
Longitude Number 5
Aliases Single-Line Text  

For each search result that represents a Flight item, you may want to display additional fields, such as the related Departure Airport City or Departure Airport Code field. To do that, you need to create a computed field.

Step 1: Configuring the Computed Field

You must first configure your computed field in the Coveo Search Provider configuration file.

  1. Using a text editor, open the Coveo.SearchProvider.Custom.config file (typically located under App_Config\Include\Coveo).

  2. Locate the fields element with a hint attribute equal to raw:AddComputedIndexField.

  3. Insert the configuration required for your computed field as shown below (that is, just the inner field element).

     <fields hint="raw:AddComputedIndexField">
   <field fieldName="departureairportcity" sourceField="Departure Airport" referencedFieldName="City">Coveo.SearchProvider.ComputedFields.ReferencedFieldComputedField, Coveo.SearchProviderBase</field>
 </fields>

Available Options

Here are the available options for your computed field:

Name Description Example value
fieldName The name of the new field to create departureairportcity
sourceField The field containing the referenced item's ID Departure Airport
referencedFieldName The name of the field on the referenced item City
returnType Return type of the field The possible values are: Integer, Number, date, and datetime.

Its value should be formatted as <complete name of the class including namespace>, <assembly>.

Since you can customize a computed field like any other field and you can make it sortable, it supports many features, such as free-text search, etc. For more information, see FieldMap. Note that in such a field map, fieldName must have the same value as the one defined in the previous section.

Step 2: Rebuilding Your Indexes

To be able to use your newly created computed field, you now need to rebuild your Sitecore indexes.

  1. Access the Indexing Manager of Sitecore (Sitecore Desktop > Start Menu > Control Panel > Indexing > Indexing Manager).

  2. Rebuild your indexes.

In this example, Flight items should now have a field named departureairportcity that contains the city of the departure airport associated with the flight.

Step 3: Using the Computed Field

Once you have rebuilt your indexes, you should be able to use your computed field in your layouts and sublayouts, just like any other Sitecore field. To refer to it, remember that you need to use the custom extension function named ToCoveoFieldName.