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Get all objects available on polymorphic field

Polymorphic Fields In Salesforce
Polymorphic Fields In Salesforce

In salesforce there is concept called polymorphic fields. Its a lookup relationship type field with more than more one object. Unlike Lookup and Master-detail relationships which are related to a single object, Polymorphic keys can refer to multiple objects. This article is based on polymorphic fields where we will discuss following topics.

Scenario :

  • How to get all lookup objects present of Polymorphic field.
  • Find all objects present on Related To (WhatId) field of Task Object 
  • Find all objects present on WhoId field of Task Object 
  • working on polymorphic lookup field in salesforce

Objects present on Task->WhatId

polymorphic fields in salesforce

Get all Objects from Task->WhatId 

				
					Map < String, Schema.SObjectType > describeResult = Schema.getGlobalDescribe();
Map < String, String > mapOfObjects = new Map < String, String > ();
Schema.DescribeFieldResult describeField;
for (Schema.SObjectField strFld: describeResult.get('Task').getDescribe().fields.getMap().Values()) {
  describeField = strFld.getDescribe();
  if (describeField.getType() == Schema.DisplayType.REFERENCE && describeField.getName() == 'WhatId') {
    for (Schema.SObjectType reference: describeField.getReferenceTo())
      mapOfObjects.put(reference.getDescribe().getName(), reference.getDescribe().getLabel());
  }
}

System.debug('mapOfObjects ' + mapOfObjects);

Objects present on Task->Who

polymorphic objects in salesforce

Get all Objects from Task->WhoId

				
					Map < String, Schema.SObjectType > describeResult = Schema.getGlobalDescribe();
Map < String, String > mapOfObjects = new Map < String, String > ();
Schema.DescribeFieldResult describeField;
for (Schema.SObjectField strFld: describeResult.get('Task').getDescribe().fields.getMap().Values()) {
  describeField = strFld.getDescribe();
  if (describeField.getType() == Schema.DisplayType.REFERENCE && describeField.getName() == 'WhoId') {
    for (Schema.SObjectType reference: describeField.getReferenceTo())
      mapOfObjects.put(reference.getDescribe().getName(), reference.getDescribe().getLabel());
  }
}

System.debug('mapOfObjects ' + mapOfObjects);

Related List

What is a polymorphic field?

A polymorphic field is a lookup that can point to more than one object. On Task, WhoId can point to a Contact or a Lead, and WhatId can point to Account, Opportunity, Case and many other objects. This is why you cannot write a simple parent relationship query for them.

How the code works

The code loops through all fields of Task and, when it finds a reference field called WhatId, calls getReferenceTo(). That method returns the list of objects the field can point to. Each object name and label is stored in a Map and printed.

Shorter version

Schema.DescribeFieldResult f = Task.WhatId.getDescribe();
for (Schema.SObjectType t : f.getReferenceTo()) {
    System.debug(t.getDescribe().getName() + ' - ' + t.getDescribe().getLabel());
}

Using the field token Task.WhatId removes the need to loop over every field. Replace it with Task.WhoId to list the objects behind WhoId.

FAQ

How can I check whether a field is polymorphic?
Call getDescribe().getReferenceTo().size(). If it is more than 1, the field points to several objects.

Which other standard fields are polymorphic?
OwnerId on some objects (User or Queue), and fields such as WhatId on Event are common examples.

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