Inheritance in Lightning Components

SK_AccountList.cmp

<aura:component controller="SK_AccountListController" extends="c:SK_CallToServerUtility">  
    <aura:attribute type="Object" name="returnedRecords" />
    <aura:attribute type="string" name="searchValue" default="" />
    <aura:set attribute="msg" value="SK_CallToServerUtility component is inherited in SK_AccountList Component"/>
    <aura:handler name="init" value="{!this}" action="{!c.doInit}"/>
    <div>
        <div class="slds-align--absolute-center">
        	Inherited Component attribute (msg) value set by this component:<b>{!v.msg}</b>
        </div>
        <br/>
        <div >
        	<lightning:input type="text" label="Enter Account Name" name="schval" value="{!v.searchValue}" aura:Id="schtxt"/>
            <lightning:button label="Search Account" variant="brand" aura:Id="btn1"  onclick="{!c.searchAccounts}"/>
        </div>
        <br/>
        <div class="slds-align--absolute-center">
            <table aura:id="accview" class="slds-table slds-table--bordered slds-table--cell-buffer" cellspacing="0" width="100%">
                <thead> 
                    <tr class="slds-text-title--caps">
                        <th scope="col">Account name</th>
                        <th scope="col">Account Type</th>
                        <th scope="col">Account Industry</th>
                    </tr>
                </thead>
                 <tbody>
                    <aura:iteration items="{!v.returnedRecords}" var="rec">
                        <tr>
                            <td>{!rec.Name}</td>
                            <td>{!rec.Type}</td>
                            <td>{!rec.Industry}</td>
                        </tr>
                    </aura:iteration>
                </tbody>
            </table>
        </div>
        
    </div>
	
</aura:component>

SK_AccountListController.apxc

public class SK_AccountListController {
    @AuraEnabled
    public static List<Account> findAccounts(string acname){
        system.debug('********acname:'+acname);
        List<Account> accList = new List<Account>();
        string searchText= string.escapeSingleQuotes(acname);
        searchText = '%' + searchText + '%';
        string queryString = '';
        if(acname != null && acname != ''){
            queryString = queryString + 'select id,name,type,industry from Account where name Like : searchText order by LastModifiedDate DESC Limit 10';
        }else{
            queryString = queryString + 'select id,name,type,industry from Account order by LastModifiedDate DESC Limit 100';
        }
        try{
            accList = database.query(queryString);
        }catch(exception ex){
            system.debug('Problem with SOQL Query:'+ ex.getMessage());
        }
        return accList;
    }

}

SK_AccountListController.js

({
    doInit : function(component, event, helper) {
		console.log('searchAccounts get called in doInit');
        helper.callToServer(
            component,
            "c.findAccounts",
            function(response) {
                console.log(' Response in SK_AccountList doInit:'+ JSON.stringify(response));
                var apexResponse = response;
                component.set("v.returnedRecords", apexResponse);
            }, 
            {
            	acname: component.get("v.searchValue")
            }
        ); 
	},
	searchAccounts : function(component, event, helper) {
		console.log('searchAccounts get called');
        helper.callToServer(
            component,
            "c.findAccounts",
            function(response) {
                console.log(' Response in SK_AccountList searchAccounts:'+ JSON.stringify(response));
                var apexResponse = response;
                component.set("v.returnedRecords", apexResponse);
            }, 
            {
            	acname: component.get("v.searchValue")
            }
        ); 
	}
})

SK_CallToServerUtility.cmp

<aura:component extensible="true">
    <!-- below attribute value will be set by components which will inherit it-->
    <aura:attribute name="msg" type="String" default=""/>
	{!v.body}
</aura:component>

SK_CallToServerUtilityHelper.js

({
	callToServer : function(component, method, callback, params) {
    console.log('Calling callToServer function in SK_CallToServerUtility extensible Component');
		var action = component.get(method);
        if(params){
            action.setParams(params);
        }
        //console.log(JSON.stringify(params));
        action.setCallback(this, function(response) {
            var state = response.getState();
            if (state === "SUCCESS") {
                //alert('Processed successfully at server');
                callback.call(this,response.getReturnValue());
                
            }else if(state === "ERROR"){
                alert('Problem with connection. Please try again.');
            }
        });
		$A.enqueueAction(action);
    }
})

SK_TestApp.app

<aura:application extends="force:slds">
    <c:SK_AccountList />
</aura:application>