MongoDB findOne error in for loop

Question

function ParseOrderSchema(CartItems , callback)
{
    var lookup = 0;
    var subOrderList = new Array();

    for(var i=0;i<CartItems.length;i++)
    {
        Meal.findOne({ _id: CartItems[i].id }).lean().exec(function (err, meal) {

            console.log(CartItems[i]);
            //meal.mealQTY = CartItems[i].qty;
            var s = new subOrder({ meals: meal, deliveryDate: getMomentDate(0) });
            subOrderList.push(s);

            if (++lookup == CartItems.length) callback(subOrderList);
        });
    }
}

At CartItem[i].id it works fine and is able to work fine. But it fails at this line meal.mealQTY = CartItems[i].qty;

It can't recognize CartItems[i] inside the findOne() method.

Can you show us the Meal schema?

chridam
– chridam

2015-06-24 20:33:07 +00:00
Commented Jun 24, 2015 at 20:33 — chridam
– chridam, Commented Jun 24, 2015 at 20:33
It is a simple schema with meal name and quantity

Shouvik S Mazumdar
– Shouvik S Mazumdar

2015-06-24 20:34:07 +00:00
Commented Jun 24, 2015 at 20:34 — Shouvik S Mazumdar
– Shouvik S Mazumdar, Commented Jun 24, 2015 at 20:34
And is there any way to resolve this ?

Shouvik S Mazumdar
– Shouvik S Mazumdar

2015-06-24 20:44:32 +00:00
Commented Jun 24, 2015 at 20:44 — Shouvik S Mazumdar
– Shouvik S Mazumdar, Commented Jun 24, 2015 at 20:44

JohnnyHK · Accepted Answer · 2015-06-24 21:03:36Z

3

Because findOne is async, i will always be CartItems.length inside the callback as the for loop runs to completion before any of the findOne callbacks occur.

You can fix this by iterating over CartItems using forEach instead so that each iteration's element is captured in a local function parameter:

function ParseOrderSchema(CartItems, callback) {
    var lookup = 0;
    var subOrderList = new Array();

    CartItems.forEach(function(cartItem) {
        Meal.findOne({ _id: cartItem.id }).lean().exec(function (err, meal) {

            console.log(cartItem);
            meal.mealQTY = cartItem.qty;
            var s = new subOrder({ meals: meal, deliveryDate: getMomentDate(0) });
            subOrderList.push(s);

            if (++lookup == CartItems.length) callback(subOrderList);
        });
    });
}

answered Jun 24, 2015 at 21:03

JohnnyHK

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1 Comment

Shouvik S Mazumdar Over a year ago

This works Thank You. Moving from Sync prog. to Async seems more challenging than previously anticipated :)

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