Firebase array always return false

Question

I'm creating an application with ionic and firebase. I'm trying to verify if a element exists in my array, and if it does, I need to return true, else I need to return false. The problem is, it always return false, even if the item exists in firebase. Can you please tell me what is going wrong with following code?

Here's my service:

function IsReserved(id){
    var ref = fb.child('/reserved/').orderByChild('product').equalTo(id);
    ref.once("value").then(function(snapshot){
        snapshot.forEach(function(data){
            if(data.val().user === $rootScope.currentUser.$id){
                console.log(data.val().user + " * " + $rootScope.currentUser.$id);
                return true;
            }
        });
    });

    return false;
}

Here is my controller:

function Reservar(produto) {
if(!$rootScope.cart){
  $rootScope.cart = [];
  $rootScope.fprice = 0;
}

var user=$rootScope.currentUser;
var res = vm.IsReserved(produto.$id);
console.log(res);


if(res){
    console.log("já reservado");                
    return;
}

Here is my firebase strucure:

-reserved:
     --KdS2cH1OJ5MhKAV6Yio:
            -product: "product1"
            -user: "W30BB1RMg1XhNo9og9cMo4Gpr4S2"

Please post a snippet of your Firebase structure, as text please, no images. — Jay
– Jay, Commented Feb 21, 2017 at 13:01
-reserved --KdS2cH1OJ5MhKAV6Yio -product: "produtc1" -user: "W30BB1RMg1XhNo9og9cMo4Gpr4S2" — Lucas Gaspar
– Lucas Gaspar, Commented Feb 21, 2017 at 13:03

Frank van Puffelen · Accepted Answer · 2017-02-21 14:25:42Z

2

Your code won't work because firebase works asynchronously.

You should use a callback function as a parameter, something like this:

function IsReserved(id, callback){
            var ref = fb.child('/reserved/').orderByChild('product').equalTo(id);
            ref.once("value").then(function(snapshot){
                snapshot.forEach(function(data){
                    if(data.val().user === $rootScope.currentUser.$id){
                        console.log(data.val().user + " * " + $rootScope.currentUser.$id);
                        callback(true);
                        return;
                    }
                });
            });
            
            return false; //-- This will always be executed before the code inside the .then, that's why your function always returns false
        }

And on you controller, something like this:

function Reservar(produto)
        {
            if(!$rootScope.cart){
              $rootScope.cart = [];
              $rootScope.fprice = 0;
            }

            var user=$rootScope.currentUser;
            vm.IsReserved(produto.$id, function(response){
               console.log(response);
               if(response){
                console.log("já reservado");                
               }
            });
  }

Could you understand?

edited Feb 21, 2017 at 14:25

Frank van Puffelen

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answered Feb 21, 2017 at 13:13

Alexandre Justino

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3 Comments

Lucas Gaspar Over a year ago

The source works, But the forEach needs to break and it return true. Your source doesn't brake, any idea? (Are you BR?)

digit Over a year ago

@LucasGaspar, you should comment/remove return false and if(data.val().user === $rootScope.currentUser.$id) should return 1 record not multiple, if not, then the code must be rewrite to add break in forloop

Alexandre Justino Over a year ago

@LucasGaspar Sim, BR! I think you can just add a return; after calling the callback inside the forEach.

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