Get components of a compound field?

Question

I am currently running into this limitation of Custom Metadata:

Custom Metadata Relationships and Compound Fields

Since it is still not possible to relate a record to a specific EntityParticle (e.g. BillingStreet) rather than the entire FieldDefinition (e.g. BillingAddress), I would like to know if it is possible to get the component fields which make up a compound field via Apex, with no callouts.

Desired state:

public static List<SObjectField> getEntityParticles(SObjectField field)
{
    List<SObjectField> particles = new List<SObjectField>();
    if (fieldIsCompound)
    {
        // get the fields which make up the compound field specified
        // without using any callouts
    }
    return particles;
}

Answer 1

If you DO know the object and field name and just wanna find components of the field, you can use:

public static String[] getComponentFields(String sobjectType, String addressFieldName) {
    EntityParticle[] particles = [
        SELECT QualifiedApiName
        FROM EntityParticle
        WHERE EntityDefinitionId = :sobjectType AND IsComponent = TRUE AND DeveloperName = :addressFieldName
    ];
    String[] ret = new String[]{};
    for(EntityParticle i: particles){
        ret.add(i.QualifiedApiName);
    }
    return ret;
}

Example

Executing:
======================================================================
System.debug(Objects.getComponentFields('Account', 'BillingAddress'));
======================================================================
Success.

14:42:55.120 (197861706)|USER_DEBUG|[1]|DEBUG|(BillingStreet, BillingCity, BillingState, BillingPostalCode, BillingCountry, BillingLatitude, BillingLongitude, BillingGeocodeAccuracy)

Answer 2

Yes, by using JSON serialization or by referencing an undocumented property compoundFieldName on Schema.DescribeFieldResult.

The API version of a field describe result includes this key. If non-null, the present field is a component of a compound field, whose API name is populated in that key.

This field is not (documented to be) available on Schema.DescribeFieldResult, but if you serialize the object, the data is present. Additionally, it can be referenced in Apex, even through it's undocumented:

Contact.OtherStreet.getDescribe().compoundFieldName

or

Contact.OtherStreet.getDescribe().getCompoundFieldName()

Hence, an approach like this is possible:

public class CompoundFieldUtil {
    public static List<SObjectField> getEntityParticles(SObjectType objectType, SObjectField field) {
        Map<String, SObjectField> fieldMap = objectType.getDescribe().fields.getMap();
        List<SObjectField> components = new List<SObjectField>();
        String thisFieldName = field.getDescribe().getName();

        for (String s : fieldMap.keySet()) {
            if (fieldMap.get(s).getDescribe().compoundFieldName == thisFieldName) {
                components.add(fieldMap.get(s));
            }
        }

        return components;
    }
}

Then,

System.debug(CompoundFieldUtil.getEntityParticles(Contact.sObjectType, Contact.OtherAddress));

yields

14:15:14:523 USER_DEBUG [1]|DEBUG|(OtherStreet, OtherCity, OtherState, OtherPostalCode, OtherCountry, OtherStateCode, OtherCountryCode, OtherLatitude, OtherLongitude, OtherGeocodeAccuracy)

The JSON serialization form also works, but is approximately five times slower:

public class CompoundFieldUtil {
    public static List<SObjectField> getEntityParticles(SObjectType objectType, SObjectField field) {
        Map<String, SObjectField> fieldMap = objectType.getDescribe().fields.getMap();
        List<SObjectField> components = new List<SObjectField>();
        String thisFieldName = field.getDescribe().getName();

        for (String s : fieldMap.keySet()) {
            Map<String, Object> describeData = (Map<String, Object>)JSON.deserializeUntyped(
                JSON.serialize(fieldMap.get(s).getDescribe())
            );

            if (describeData.containsKey('compoundFieldName')
                && (String)describeData.get('compoundFieldName') == thisFieldName) {
                components.add(fieldMap.get(s));
            }
        }

        return components;
    }
}