Custom Dependent Picklist Field in Salesforce using Lightning Web Components

This post explains how to implement custom dependent picklist field using lightning web components(lwc)

To get the picklist values in lightning web components we can use 'getPicklistValues' or 'getPicklistValuesByRecordType' wire adapters, these wire adapters uses the lightning/uiObjectInfoApi scoped module to get the picklist values based on specific Field or based on Record Type.

Syntax

import { getPicklistValues, getPicklistValuesByRecordType } from 'lightning/uiObjectInfoApi';

For the demo, I created two fields on Account.
Controlling Field(picklist): Account Country
Dependent Field(picklist): Account State

The structure of the dependent field

HTML Code

<template>
    <lightning-card title="Custom Dependent Picklist using Lightning Web Components"><br/>
        <div class="slds-grid slds-gutters" style="margin-left:3%">
            <div class="slds-col slds-size_1-of-4">
                <lightning-combobox label="Account Country" 
                                    name="country" 
                                    onchange={handleCountryChange} 
                                    options={controllingValues} 
                                    placeholder="--None--" 
                                    value={selectedCountry}></lightning-combobox><br/>
                
                <div if:true={selectedCountry}>
                    Selected Country: <b>{selectedCountry}</b>
                </div>
            </div>
            <div class="slds-col slds-size_1-of-4">
                <lightning-combobox label="Account State" 
                                    name="state"
                                    onchange={handleStateChange} 
                                    options={dependentValues} 
                                    placeholder="--None--" 
                                    value={selectedState}
                                    disabled={isEmpty}></lightning-combobox><br/>
                <div if:true={selectedState}>
                    Selected State: <b>{selectedState}</b>
                </div>
            </div>
        </div><br/>

        <div if:true={error}>
            <p>{error}</p>
        </div>
    </lightning-card>
</template>

Javascript Controller Code

import { LightningElement, wire, track } from 'lwc';
import { getPicklistValuesByRecordType } from 'lightning/uiObjectInfoApi';
import { getObjectInfo } from 'lightning/uiObjectInfoApi';
import ACCOUNT_OBJECT from '@salesforce/schema/Account';

export default class DependentPickListInLWC extends LightningElement {

    // Reactive variables
    @track controllingValues = [];
    @track dependentValues = [];
    @track selectedCountry;
    @track selectedState;
    @track isEmpty = false;
    @track error;
    controlValues;
    totalDependentValues = [];

    // Account object info
    @wire(getObjectInfo, { objectApiName: ACCOUNT_OBJECT })
    objectInfo;

    // Picklist values based on record type
    @wire(getPicklistValuesByRecordType, { objectApiName: ACCOUNT_OBJECT, recordTypeId: '$objectInfo.data.defaultRecordTypeId'})
    countryPicklistValues({error, data}) {
        if(data) {
            this.error = null;

            let countyOptions = [{label:'--None--', value:'--None--'}];

            // Account Country Control Field Picklist values
            data.picklistFieldValues.Account_Country__c.values.forEach(key => {
                countyOptions.push({
                    label : key.label,
                    value: key.value
                })
            });

            this.controllingValues = countyOptions;

            let stateOptions = [{label:'--None--', value:'--None--'}];

             // Account State Control Field Picklist values
            this.controlValues = data.picklistFieldValues.Account_State__c.controllerValues;
            // Account State dependent Field Picklist values
            this.totalDependentValues = data.picklistFieldValues.Account_State__c.values;

            this.totalDependentValues.forEach(key => {
                stateOptions.push({
                    label : key.label,
                    value: key.value
                })
            });

            this.dependentValues = stateOptions;
        }
        else if(error) {
            this.error = JSON.stringify(error);
        }
    }

    handleCountryChange(event) {
        // Selected Country Value
        this.selectedCountry = event.target.value;
        this.isEmpty = false;
        let dependValues = [];

        if(this.selectedCountry) {
            // if Selected country is none returns nothing
            if(this.selectedCountry === '--None--') {
                this.isEmpty = true;
                dependValues = [{label:'--None--', value:'--None--'}];
                this.selectedCountry = null;
                this.selectedState = null;
                return;
            }

            // filter the total dependent values based on selected country value 
            this.totalDependentValues.forEach(conValues => {
                if(conValues.validFor[0] === this.controlValues[this.selectedCountry]) {
                    dependValues.push({
                        label: conValues.label,
                        value: conValues.value
                    })
                }
            })

            this.dependentValues = dependValues;
        }
    }

    handleStateChange(event) {
        this.selectedState = event.target.value;
    }
}

Configuration File

<?xml version="1.0" encoding="UTF-8"?>
<LightningComponentBundle xmlns="http://soap.sforce.com/2006/04/metadata" fqn="dependentPickListInLWC">
    <apiVersion>46.0</apiVersion>
    <isExposed>true</isExposed>
    <targets>
        <target>lightning__AppPage</target>
        <target>lightning__RecordPage</target>
        <target>lightning__HomePage</target>
    </targets>
</LightningComponentBundle>

You can also find the code on Github
GitHub Link


Result