How can we call child component controller method from parent component controller method in Salesforce?

To call a child component’s controller method, we need to first create a aura:method which is publically accessible, aura:method is used to communicate down the containment hierarchy i.e. parent to child. Sample code for implementing the aura method:
Component code

Controller
({
publicmethod: function(cmp, event) {
var params = event.getParam(‘arguments’);
if (params) {
var message = params. str;
console.log(“message: ” + message);
return message;
}
}
})

Calling the cild method from parent controller
({
callchildCompMethod : function(component, event, helper) {
var childCmp = component.find(“childCompName”);
var Result =
childCmp. publicmethod (“message sent by parent component”);
console.log(“Result: ” + Result);
}
})