Suppose I have two custom objects: Property and Broker. Property has a lookup field to Broker. Suppose now I need to create a custom aura component inside a property record page that shows only the empty fields of the Broker lookup record in a lightning:recordForm. Using LDS I could declare two attributes:

<aura:attribute name="recordId" type="Id" />
<aura:attribute name="simpleRecord" type="Object" />

And a <force:recordData> tag to get the fields from that property record:

<force:recordData aura:id="recordLoader"
        recordUpdated="{!c.recordUpdated}" />

I could show the Broker fields by using lightning:recordForm:

<lightning:card iconName="standard:user" title="{! 'Broker for ' + v.simpleRecord.Name}">
        <div class="slds-p-left_large slds-p-right_medium">
            <lightning:recordForm aura:id="brokerForm" mode="VIEW" recordId="{!v.simpleRecord.Broker__c}"
                columns="2" />

But I need to only show the fields which are empty. I can do something like this in the Javascript Controller, but I need to get the fields from the Broker record, not the Property record:

recordUpdated: function (component, event, helper) {

        var eventParams = event.getParams();

        if (eventParams.changeType === "LOADED") {
            // record is loaded (render other component which needs record data value)

            const json = JSON.parse(JSON.stringify(component.get('v.simpleRecord')));
            let emptyFields = []

            for (const [fieldName, fieldInfo] of Object.entries(json.fields)) {
                if (fieldInfo.value === null) {

            console.log('emptyFields: ', emptyFields);


Also, in the json I can see some of the Broker fields inside the Broker__r value, but only Id and Name.

In summary, how do I get the fields from a related object, but only the empty fields, using only Lightning Data Service, not apex?

Thanks for your attention.

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