InterlockSelector ( lightning component which is a sObjects selector and is a field selector which interlocks with specified sObject )

InterlockSelector.cmp

<aura:component controller="InterlockSelectorController">
    <aura:attribute name="objectName" type="String"/>
    <aura:attribute name="fieldName" type="String"/>
    <aura:attribute name="required" type="Boolean" default="false"/>

    <aura:attribute name="objectOptions" type="List" default="[]"/>
    <aura:attribute name="fieldOptions" type="List" default="[]"/>

    <aura:handler name="init" value="{!this}" action="{!c.init}" />
    <aura:handler name="change" value="{!v.objectName}" action="{!c.changeNameAttribute}"/>
    <aura:handler name="change" value="{!v.fieldName}" action="{!c.changeNameAttribute}"/>

    <lightning:combobox aura:id="object" name="object" label="target object" value="{!v.objectName}" required="{!v.required}" placeholder="select target object." options="{!v.objectOptions}" onchange="{!c.selectObject}"/>
    <aura:renderIf isTrue="{!v.objectName}">
        <lightning:combobox aura:id="field" name="field" label="target field" value="{!v.fieldName}" required="{!v.required}" placeholder="select target field" options="{!v.fieldOptions}" onchange="{!c.selectField}"/>
    </aura:renderIf>
</aura:component>

InterlockSelectorController.cls

public with sharing class InterlockSelectorController {
    @AuraEnabled
    public static  List<Map<String, String>> getObjects() {
        List<Map<String, String>> sobjectList = new List<Map<String, String>>();
        List<EntityDefinition> entityDefinitions = [SELECT label, MasterLabel, QualifiedApiName FROM EntityDefinition WHERE IsLayoutable = true AND IsQueryable = true Order by MasterLabel];
        for (EntityDefinition ed: entityDefinitions) {
            Map<String, String> sobjectInfo = new Map<String, String>();
            sobjectInfo.put(ed.QualifiedApiName, ed.label);
            sobjectList.add(sobjectInfo);
        }
        return sobjectList;
    }

    @AuraEnabled
    public static Map<String, String> getFields(String objectApiName) {
        Map<String, String> retVal = new Map<String, String>();
        Map<String, Schema.SObjectField> fieldMap = Schema.getGlobalDescribe().get(objectApiName).getDescribe().fields.getMap();
        List<String> fieldNames = new List<String>(fieldMap.keySet());
        fieldNames.sort();
        for (String fieldName: fieldNames) {
            retVal.put(fieldName, fieldMap.get(fieldName).getDescribe().getLabel());
        }
        return retVal;
    }
}

InterlockSelectorController.js

({
    init : function(component, event, helper) {
        helper.fetchObjectComboboxValue(component);
        let changeNameAttribute = component.get('c.changeNameAttribute');
        $A.enqueueAction(changeNameAttribute);
    },
    selectObject: function (component, event, helper) {
        let selectedOptionValue = event.getParam("value");
        component.set("v.objectName", selectedOptionValue);
        if (selectedOptionValue === "") {
            component.set("v.fieldName", "");
        }           
        helper.fetchFieldComboboxValue(component, selectedOptionValue); 
    },
    selectField: function (component, event, helper) {
        let selectedOptionValue = event.getParam("value");
        component.set("v.fieldName", selectedOptionValue);
    },
    changeNameAttribute : function(component, event, helper) {
        component.find("object").set("v.value", component.get("v.objectName"));
        helper.fetchFieldComboboxValue(component, component.get("v.objectName"));
        component.find("field").set("v.value", component.get("v.fieldName"));
    }
})

InterlockSelectorHelper.js

({
    fetchObjectComboboxValue : function(component) {
        let action = component.get("c.getObjects");
        let opts = [];
        action.setCallback(this, function(response) {
            if (response.getState() == "SUCCESS") {
                let values = response.getReturnValue();
                if (values != undefined && values.length > 0) {
                    opts.push({
                        label: "--- None ---",
                        value: ""
                    });
                }
                for (let i = 0; i < values.length; i++) {
                    Object.keys(values[i]).forEach(function(key) {
                        let value = values[i][key];
                        opts.push({
                            label: value,
                            value: key
                        });
                    });
                }
                component.set("v.objectOptions", opts);
            }
        });
        $A.enqueueAction(action);
    },
    fetchFieldComboboxValue : function(component, objectApiName) {
        let action = component.get("c.getFields");
        action.setParams({
            "objectApiName": objectApiName
        });
        let opts = [];
        action.setCallback(this, function(response) {
            if (response.getState() == "SUCCESS") {
                var fieldMap = response.getReturnValue(); 
                for (var k in fieldMap) {
                    opts.push({ value:k, label:fieldMap[k]});
                }
                component.set("v.fieldOptions", opts);
            }
        });
        $A.enqueueAction(action);
    }
})