How to display Task WhatId related field on Lightning Page

Question

Apex Controller:

public without sharing class DTask {
    @AuraEnabled
    public static List<Task> getTaskList(){

        Id userId = UserInfo.getUserId();
        User loggedInUser = [Select Id, Email, ProfileId From User Where Id = :userId];

        List<Task> taskList = [Select Id, Subject, ActivityDate, Status, Created_DateTime__c, subjectType__c
                               From Task
                               Where OwnerId = :userId Limit 10
                              ];       
        return taskList;
    }    

    @AuraEnabled
    public static list < Task > fetchTasks(String sortField, boolean isAsc) {
        Id userId = UserInfo.getUserId();
        User loggedInUser = [Select Id, Email, ProfileId From User Where Id = :userId];

        String statusCompleted = 'Completed';
        String subType = 'Follow Up';


        String sSoql = 'SELECT Id, Subject, ActivityDate,Created_DateTime__c, Status , WhoId, WhatId, Who.Name, What.Name,   subjectType__c ';
        sSoql += 'From Task Where OwnerId = :userId And Status != \'' +String.escapeSingleQuotes(statusCompleted)+'\'  AND subjectType__c  = \'' +String.escapeSingleQuotes(subType)+'\'   ';
               --------            return returnTaskList;        
   }      
}

Lightning Component:

<aura:component implements="force:appHostable,flexipage:availableForAllPageTypes,flexipage:availableForRecordHome,forceCommunity:availableForAllPageTypes"
                controller="DTask">
    <aura:attribute name="taskList" type="List"/>
    <aura:attribute name="taskStatusList" type="List"/>
    <aura:attribute name="selectStatus" type="String"/>
    <aura:attribute name="options" type="List" />

    <aura:attribute name="arrowDirection" type="string" default="arrowup" description="Use for change arrow sign direction on header based on click"/>
    <aura:attribute name="isAsc" type="boolean" default="true" description="boolean flag for pass sorting condition to apex class"/>
    <aura:attribute name="selectedTabsoft" type="string" default="DueDate" description="Use for show/hide arraow sign on header based on conditions"/>


    <aura:handler name="init" value="{!this}" action="{!c.doInit}"/>
    <aura:dependency resource="markup://force:navigateToSObject" type="EVENT"/>

    <aura:handler event="force:navigateToSObject" action="{!c.navigateToRecord}"/>

    <lightning:card title="Tasks Due">
        <table style="width: 100%; table-layout:fixed;" class="slds-table slds-table_bordered slds-table_cell-buffer slds-max-medium-table_stacked-horizontal slds-cell-wrap">
            <thead>
                <tr class="slds-text-heading--label">
                    <th class="" style = "width: 30%;" scope="col">Subject</th>

                    <th class="" style = "width: 20%;" scope="col"  onclick="{!c.sortDueDate}">
                        <a href="javascript:void(0);" class="slds-th__action slds-text-link--reset">
                            <span class="slds-assistive-text">Sort</span>
                            <span class="slds-truncate" title="Name">Created Date</span>
                            <aura:if isTrue="{! and(v.arrowDirection == 'arrowdown', v.selectedTabsoft == 'DueDate') }">&nbsp;  &#9660; </aura:if>
                            <aura:if isTrue="{! and(v.arrowDirection != 'arrowdown', v.selectedTabsoft == 'DueDate') }"> &nbsp;  &#9650; </aura:if>
                        </a>
                    </th>

                    <!--Added New -->                   
                    <th class="" style = "width: 15%;" scope="col"  onclick="{!c.sortDueDate2}">
                        <a href="javascript:void(0);" class="slds-th__action slds-text-link--reset">
                            <span class="slds-assistive-text">Sort</span>
                            <span class="slds-truncate" title="Name">Due Date</span>
                            <aura:if isTrue="{! and(v.arrowDirection == 'arrowdown', v.selectedTabsoft == 'DueDate') }">&nbsp;  &#9660; </aura:if>
                            <aura:if isTrue="{! and(v.arrowDirection != 'arrowdown', v.selectedTabsoft == 'DueDate') }"> &nbsp;  &#9650; </aura:if>
                        </a>
                    </th>


                    <th class="" style = "width: 20%;" scope="col">Status</th>
                    <th class="" style = "width: 20%;" scope="col">Name </th>
                    <th class="" style = "width: 20%;" scope="col">Related To </th>                    
                </tr>
            </thead>
            <tbody>
                <aura:iteration items="{!v.taskList}" var="task">
                    <tr class="slds-hint-parent slds-cell-wrap">
                        <td data-label="Subject" class="slds-cell-wrap" >
                            <a onclick="{!c.navigateToRecord}" style="width:100%;" data-index="{!task.Id}">{!task.Subject}</a>
                        </td>

                        <td data-label="Created Date" class="slds-cell-wrap" >  
                            <ui:outputDate value="{!task.Created_DateTime__c}" format="MM/dd/YYYY, hh:mm A"></ui:outputDate>                           
                        </td> 

                        <!--Added New -->
                        <td data-label="Due Date" class="slds-cell-wrap" >  
                            <ui:outputDate value="{!task.ActivityDate}" format="MM/dd/YYYY"></ui:outputDate>                           
                        </td> 

                        <td data-label="Status" data-taskId="{!task.Id}" id="tdId" class="tdclass">
                            <lightning:select name="{!task.Id}" label="" aura:id="{!task.Id}" value="{!task.Status}"
                                              variant="label-hidden" onchange="{!c.saveTaskStatusFun}">
                                <aura:iteration items="{!v.taskStatusList}" var="itemStatus">
                                    <option text="{!itemStatus}" value="{!itemStatus}" />
                                 </aura:iteration>
                            </lightning:select>

                            <lightning:input aura:id="taskId" label="taskId" name="taskId"
                                                    type="text" value="{!task.Id}"  class="slds-hide"/>
                        </td>
                        <td data-label="Name" class="slds-cell-wrap" >
                            <a onclick="{!c.navigateToName}" style="width:100%;" data-index="{!task.WhoId}">{!task.Who.Name}</a>
                        </td>
                        <td data-label="Related to" class="slds-cell-wrap" >
                            <a onclick="{!c.navigateToRelatedTo}" style="width:100%;" data-index="{!task.WhatId}">{!task.What.Name}</a>
                        </td>
                    </tr>
                </aura:iteration>
            </tbody>
        </table>
       <table style="width: 100%; table-layout:fixed;" class="slds-table slds-table_bordered slds-table_cell-buffer slds-max-medium-table_stacked-horizontal slds-cell-wrap">
        <th class="" scope="col"></th>
            <td data-label="View All" class="slds-cell-wrap" >
              <a onclick="{!c.navigateToViewAll}" style="width:100%;">View All</a>
            </td> 
       </table>
    </lightning:card>
</aura:component>

Output:

Related To: is a Custom Object. I am getting Name of Related Object but I want to display a different field from Related Object Bank__c(Related Object), Bank_Status__c(field on related object). How can I query this value in controller and display it on lightning component. I tried WhatId.Bank_Status__c , WhatId.Name.Bank_Status__c nothing worked can someone help me with this,

All I want is related object data(not just name) to be displayed in my component.

Thanks much!

Answer 1

WhatId is a polymorphic lookup field: it can refer to many different object types. Unless your org has the special SOQL Polymorphism feature turned on, you need to structure your relationship queries differently than standard SOQL dot notation.

Across the WhatId relationship, you can access at least the Type and Name fields with simple dot notation (SELECT What.Name, What.Type FROM Task WHERE ...). However, if you want more data, you'll have to perform an entirely separate query that will vary by the type of the What entity.

For your use case, what you'd have to do is, first, establish that the What entity is a Bank__c, by either inspecting the What.Type or looking at the Id's key prefix, and then perform a Bank__c query separately:

SELECT Bank_Status__c FROM Bank__c WHERE Id IN :myWhatIds

(This assumes that you've accumulated your WhatIds in a Set).

Getting this data back into Lightning from your server-side controller might involve using a wrapper class.