Using Promises In Lightning

LightningComponentController.js

{
	
	doInit : function(component, event , helper){
		var action = cmp.get("c.getCurrentUser");
		action.setCallback(this, function(response) {
			var state = response.getState();
			if (state === "SUCCESS") {
				component.set("v.user", response.getReturnValue());
			}
			else {
				alert('error');
			}
		})
	}
}

LightningComponentExtendedController.js

{
	
	doInit : function(component, event , helper){
		var action = cmp.get("c.getCurrentUser");
		action.setCallback(this, function(response) {
			var state = response.getState();
			if (state === "SUCCESS") {
				component.set("v.user", response.getReturnValue());
			}
			else {
				alert('error');
			}

			action = cmp.get("c.getCases");
			action.setCallback(this, function(response) {
				var state = response.getState();
				if (state === "SUCCESS") {
					component.set("v.cases", response.getReturnValue());
				}
				else {
					alert('error');
				}
			});
		})
	}
}

LightningCtrl.cls

public class LightningCtrl {
	@AuraEnabled
	public static User getCurrentUser(){
		return [
			SELECT Id, Name, ContactId, AccountId
			FROM User
			WHERE Id =:UserInfo.getId()
		];
	}
	
	@AuraEnabled
	public static List<Case> getCases(){
		return [
			SELECT Id, CaseNumber, Subject
			FROM Case 
			WHERE OwnerId =:UserInfo.getId()
		];
	}
}

LightningPromiseComponentCatchController.js

{
	
	doInit : function(component, event , helper){

		helper.call(component.get("c.getCurrentUser")).then(function(user){
			// called when the method was successful
			component.set("v.user", user);
		}).catch(function(err) {
			alert('error')
		})
		
	},

}

LightningPromiseComponentController.js

{
	
	doInit : function(component, event , helper){

		helper.call(component.get("c.getCurrentUser")).then(function(user){
			// called when the method was successful
			component.set("v.user", user);
		},function(err){
			// error handler
			alert('error');
		})
		
	}
}

LightningPromiseComponentExtendedCatchController.js

{
	
	doInit : function(component, event , helper){

		helper.call(component.get("c.getCurrentUser")).then(function(user){
			// called when the method was successful
			component.set("v.user", user);
			return component.call(component.get("c.getCases"))
		}).then(function(cases){
			component.set("v.cases", cases);
		}).catch(function(err) {
			alert('error')
		})
	}
}

LightningPromiseComponentHelper.js

{
	call: function(action, params) {
        return new Promise($A.getCallback(function(resolve, reject) {
            if (params) {
                action.setParams(params);
            }
            action.setCallback(this, function(a) {
                var err = a.getError();
                var result = a.getReturnValue();
                if (err && err.length > 0) reject(err);
                else resolve(result);
            });
            $A.enqueueAction(action, false);
        }));

    }

}