How to use v.sObjectName to define fields in Lightning Data Service

Question

To use my Lightning component for record pages of multiple types I need to load the record in a generic fashion.

<aura:component controller="MyCtrl" implements="force:hasRecordId,force:hasSObjectName,...">
    <aura:attribute name="record" type="Map" />

    <force:recordData recordId="{!v.recordId}" targetRecord="{!v.record}"
                      fields="{!(v.SObjectName == 'NS__MyObject__c') ? 'NS__lkp_Parent__c' : 'Id'}" />
    ...
</aura:component>

Not all of those type have a specific field called NS__lkp_Parent__c. Lightning Data Service refused (fail) to load the whole record when I pass non-existing fields (which is bad!). Therefor I added a condition that checks the SObjectName before.

But this also fails with a generic error:

Unfortunately, there was a problem... Action failed: forceChatter:lightningComponent$controller$doInit [Error while creating content for lightning component quick action] quickActionHandlerHelper.js failed to create component - forceChatter:lightningComponent

What am I doing wrong?

Answer 1

I believe that your code is failing because you are returning a string value instead of an array of strings in the fields attribute (either 'NS__lkp_Parent__c' or 'Id').

Edited: looks like expressions cannot return an array in this case so the solution is to set the fields value via JS instead of using an expression.

Here are the steps:

1) add an aura:id="lds" attribute to the force:recordData component

2) add an init handler to your parent component

3) set the fields attribute in your init handler:

component.find('lds').set('v.fields', yourFieldsArray);

Answer 2

Adding the conditional directly into the fields attribute didn't work as the square brackets after the ? was not allowed to be saved.

Nonetheless the root cause mentioned by POZ was the solution. fields is not a comma-separated string but a String array of type String[].

Here is how we changed our code:

Component:

<aura:component controller="MyCtrl" implements="force:hasRecordId,force:hasSObjectName,...">
    <aura:attribute name="record" type="Map" />
    <aura:attribute name="recordFields" type="String[]" />

    <aura:if isTrue="{!v.recordFields.length > 0}">
        <force:recordData recordId="{!v.recordId}" targetFields ="{!v.record}" fields="{!v.recordFields}" />
    </aura:if>

    <aura:handler name="init" value="{!this}" action="{!c.onInit}" />
    ...
</aura:component>

Controller:

({
    onInit: function(cmp) {
        let fields = ['Id'];

        if(cmp.get("v.sObjectName") !== 'NS__MyObject__c') {
            fields.push('NS__lkp_Parent__c');
        }

        cmp.set("v.recordFields", fields);
    },
});