LWC How to Get Parent Value

Question

How do you get the parent value? I am trying to get Order_Bill_To__r.Comm_Model__c without using APEX. I thought I could do this using __r however when I run this it says that [LWC component's @wire target property or method threw an error during value provisioning. Original error: [Cannot read property 'value' of undefined]]

It is failing specifically on this line with the above error this.Order_Bill_To__r.Comm_Model__c = this.quote.fields.Order_Bill_To__r.Comm_Model__c.value

    import { LightningElement, api, wire, track } from 'lwc';
    import { getObjectInfo } from 'lightning/uiObjectInfoApi';
    import QUOTE_OBJECT from '@salesforce/schema/SBQQ__Quote__c';
    import SubmitQuoteForApproval from '@salesforce/apex/clsSubmitObjectForApproval.SubmitForApproval';
    const FIELDS = ['SBQQ__Quote__c.Order_Bill_To__r.Comm_Model__c', 'SBQQ__Quote__c.RecordTypeId', 'SBQQ__Quote__c.SBQQ__LineItemCount__c'];
    import { getRecord } from 'lightning/uiRecordApi';
    import { ShowToastEvent } from 'lightning/platformShowToastEvent';
    import { CloseActionScreenEvent } from 'lightning/actions';
    import { getRecordNotifyChange } from 'lightning/uiRecordApi';
    import { updateRecord } from 'lightning/uiRecordApi';
    import ID_FIELD from '@salesforce/schema/SBQQ__Quote__c.Id';

    export default class LwcSubmitQuoteToOrder extends LightningElement {

        @api recordId;
        @api objectApiName;
        @track quote;
        @track ValidationMessage;
        @track recordType;
        @track objectInfo;


        @wire(getObjectInfo,  { objectApiName: QUOTE_OBJECT })
        ObjectInfo;
      
        @wire(getRecord, { recordId: '$recordId', fields: FIELDS })
        wiredRecord({error, data }) {
            if(data) {
                this.quote = data;
                this.SBQQ__LineItemCount__c = this.quote.fields.SBQQ__LineItemCount__c.value;
                this.recordType = this.quote.fields.RecordTypeId.value;
                this.Order_Bill_To__r.Comm_Model__c = this.quote.fields.Order_Bill_To__r.Comm_Model__c.value;
                
                //Must declare that ValidationMessage be nothing. 
                this.ValidationMessage  = '';


                if(this.GetRecordTypeValue() == true){
                    this.UpdateQuote();
                }
                if(this.Order_Bill_To__r.Comm_Model__c == true){
                    this.ValidationMessage = this.ValidationMessage +  'You are submitting an order for an NSO that uses the commissioner model. ‘Transfer Price (USD)’ from the attached Ametek PO is required for all line items.\n'; 
                 }
                
            } 

        async invokeApexMethods() {
                // Update the record via Apex.
                await SubmitQuoteForApproval({idObject: this.recordId})
                // Notify LDS that you've changed the record outside its mechanisms.
                getRecordNotifyChange([{recordId: this.recordId}]);
        }
      
        closeAction(){
           this.dispatchEvent(new CloseActionScreenEvent());
        }
          
        showErrorToast(x) {
            const evt = new ShowToastEvent({
                title: 'Submit Quote For Approval',
                message: x,
                variant: 'Quote has Successfully Submitted',
                mode: 'dismissable'
            });
            this.dispatchEvent(evt);
        } 

         GetRecordTypeValue() {
            // Returns a map of record type Ids 
            const rtis = this.ObjectInfo.data.recordTypeInfos;
            const rtInfo= Object.keys(rtis).find(rti => rtis[rti].name == 'Official_Sales_Quote');
            
            if(this.RecordType===rtInfo){
                return true;
            } else{
                return false;
            }  
            
        }

        UpdateQuote(){
            const fields = {};
            fields[ID_FIELD.fieldApiName] = this.recordId;
            fields[SALESORDER_FIELD.fieldApiName] = true;
            
            const recordInput = { fields };
            updateRecord(recordInput);
        }

    }

Answer 1

Considering that you have deeply nested properties when assigning values, you might want to ensure that they are not returning undefined.

to ensure that the properties in this.quote.fields.Order_Bill_To__r.Comm_Model__c.value populated.

I would suggest you use a combination of Nullish coalescing operator (??) and use Optional chaining (?.)

Ex:

this.quote?.fields?.Order_Bill_To__r?.Comm_Model__c?.value ?? 'default value to avoid undefined'

you can also add type checking, however, given the amount of properties, you'd end up having multiple if statements which can be avoided.