How to call a child component"s method from its parent in Salesforce?

Hi Yogesh,

Use <aura:method> to define a method as part of a component's API. This enables you to directly call a method in a component’s client-side controller instead of firing and handling a component event. Using <aura:method> simplifies the code needed for a parent component to call a method on a child component that it contains.

For Example

Get Message from Child Component to parent Component.

Step 1) Create Child component with Aura:Method.

ChildCmp.cmp

<!--ChildCmp.cmp-->
<aura:component >
    <aura:method name="GetMessageFromChildMethod" action="{!c.getMessage}" 
                 access="public">
        <aura:attribute name="Name" type="String" default="Amit"/>
    </aura:method>
</aura:component>

Step 2) Create Child Class Controller to Get argument "event.getParam('arguments');" and return the message.

ChildCmpController.js

({
    getMessage : function(component, event) {
        var params = event.getParam('arguments');
        if (params) {
            var param1 = params.Name;
            return "##### Hello "+param1+" From Child Component #####";
        }
        return "";
    }
})

Step 3) Create a parent Component and a button to call Aura method.

ParentCmp.cmp

<!--ParentCmp.cmp-->
<aura:component >
    <aura:attribute name="message" type="String" 
                    default="------ Hello From Parent -----"/>
    <c:ChildCmp aura:id="childComponent"/>
   
    <div class="slds-m-around_xx-large">
        <lightning:button variant="brand" label="Call Aura Method" 
                          onclick="{!c.callAuraMethod}" />
        <BR></BR> <BR></BR>
        <p>{!v.message}</p>
    </div>
</aura:component>

Step 4) Create Parent Component Controller to Call Aura Method "childCmp.GetMessageFromChildMethod('Amit');".

ParentCmpController.js

({
     callAuraMethod : function(component, event, helper) {
            var childCmp = component.find("childComponent");
            var retnMsg = childCmp.GetMessageFromChildMethod('Amit');
            component.set("v.message", retnMsg);
     }
})

DemoApp.app

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