How to get the entity ID for a custom field in Apex?
Question
I need a way to get the 15-character entity ID for a custom field on the Lead object in an Apex controller. I tried using the following method:
private String getEntityIdFor(String fieldName) {
Map<String, Schema.SObjectField> fieldMap = Schema.SObjectType.Lead.fields.getMap();
return fieldMap.get(fieldName).getDescribe().getId();
}However, I ran into an issue since there is no getId() method available, so this approach doesn’t work. How can I retrieve the entity ID for a custom field in Apex?
Answer:
One way to retrieve the entity ID for a custom field is by using the Tooling API. You can make an HTTP request to the Tooling API to query for the custom field’s details, including the ID.
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Here’s an example of how you could do it in Apex:
HttpRequest req = new HttpRequest();
req.setHeader('Authorization', 'Bearer ' + UserInfo.getSessionID());
req.setHeader('Content-Type', 'application/json');
String toolingendpoint = 'https://na1.salesforce.com/services/data/v20.0/tooling/';
// Query for custom fields
toolingendpoint += 'query/?q=SELECT Id, DeveloperName, FullName FROM CustomField LIMIT 1';
req.setEndpoint(toolingendpoint);
req.setMethod('GET');
Http h = new Http();
HttpResponse res = h.send(req);
System.debug(res.getBody());Explanation: The code sends an HTTP GET request to Salesforce’s Tooling API to query for custom field details, specifically retrieving the Id, DeveloperName, and FullName for custom fields. It sets the authorization header using the session ID and specifies the request content type as JSON. The response from the API is captured and printed in the debug log.
Alternate approaches
Here are a couple of alternate approaches to retrieve the entity ID for a custom field in Apex.
1. Using the Tooling API
You can query the Tooling API for custom field details. This approach requires sending an HTTP request to retrieve the field information. The Tooling API is useful for getting metadata, like the Id, DeveloperName, and FullName of a custom field.
Here’s an example of how to use it in Apex:
HttpRequest req = new HttpRequest();
req.setHeader('Authorization', 'Bearer ' + UserInfo.getSessionID());
req.setHeader('Content-Type', 'application/json');
String toolingendpoint = 'https://na1.salesforce.com/services/data/v20.0/tooling/';
// Query for custom fields
toolingendpoint += 'query/?q=SELECT Id, DeveloperName, FullName FROM CustomField LIMIT 1';
req.setEndpoint(toolingendpoint);
req.setMethod('GET');
Http h = new Http();
HttpResponse res = h.send(req);
System.debug(res.getBody());Explanation: The code sends an HTTP GET request to the Salesforce Tooling API to retrieve custom field details. It includes an authorization header using the current session ID and queries for the Id, DeveloperName, and FullName of custom fields. The response is logged using System.debug to display the results from the API call.
2. Using the Schema.DescribeFieldResult
While you can’t directly retrieve the entity ID with getDescribe().getId(), you can still get useful information like the field’s name, type, and other metadata. For example, you can retrieve the full name of the custom field (which includes the entity ID as part of the API name) using the following approach:
Schema.SObjectField field = Schema.SObjectType.Lead.fields.getMap().get('CustomFieldName');
Schema.DescribeFieldResult fieldDesc = field.getDescribe();
String fieldFullName = fieldDesc.getName(); // This includes the API name with the entity ID
System.debug('Field Full Name: ' + fieldFullName);Explanation: The code retrieves the Schema.SObjectField for the custom field on the Lead object by accessing it through the field map. It then uses getDescribe() to obtain the field’s metadata and calls getName() to get the full API name, which includes the entity ID. Finally, it logs the full API name, allowing you to see both the field’s developer name and its entity ID.
This approach will give you the full API name of the custom field, which includes the entity ID. However, it doesn’t give you the 15-character ID directly.
3. Using Custom Metadata or Custom Settings
If the field IDs are something you need to reference often, consider storing the field IDs in a custom metadata type or custom setting. You can then query these records in Apex without relying on Tooling API calls. This would involve creating a custom metadata type to store field IDs and querying the metadata when necessary.
For example, create a custom metadata type Field_Reference__mdt with a field Entity_ID__c to store field IDs, and then query it in Apex:
List<Field_Reference__mdt> fieldReferences = [SELECT Entity_ID__c FROM Field_Reference__mdt WHERE DeveloperName = 'CustomFieldName'];
String fieldId = fieldReferences.isEmpty() ? null : fieldReferences[0].Entity_ID__c;
System.debug('Stored Field ID: ' + fieldId);Explanation: The code queries the custom metadata type Field_Reference__mdt for a record with a DeveloperName of ‘CustomFieldName’. It retrieves the Entity_ID__c field, which contains the field ID, and stores it in the fieldId variable. If no matching records are found, fieldId is set to null, and the result is logged using System.debug().
This approach requires you to manually maintain the field IDs in the custom metadata records but can be very useful if you need to reference these values frequently in your application.
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