CODEWITHSUNDEEP
javascriptangularjs
neptune
neptune

Reputation: 1261

Handling data from multiple data sources

Here I have a simple Angular app with two services, one getting the balance of a Dogecoin public address, the second getting the price of Dogecoin in Btc, from two different source.

Services:

angular.module('AppName', ['ngResource'])

.factory('DogeBalance', ['$resource', function ($resource) {
    return $resource("https://dogechain.info/api/v1/address/balance/:address");
}])

.factory('DogePrice', ['$resource', function ($resource) {
    return $resource("https://chain.so/api/v2/get_info/DOGE");
}])

and the controller:

.controller('TwoController', function($scope, DogeBalance, DogePrice){

    $scope.wallets = [
        { id: 0, type: 'doge', address: 'DT2rmMrutwzdZ8EXwzj4QFdcL6DtvGGkci'},
        { id: 1, type: 'doge', address: 'DMoonjyH1aHLZc1kksmikBUhjXromn1ZN4'}
    ];

    var price = DogePrice.get();
    $scope.totalBalance = parseFloat(0);

    price.$promise.then(function(data) {
        $scope.price = data.data.price;
            //aggregate balance on all the addresses
        for (i in $scope.wallets){
            var balance = DogeBalance.get({address: $scope.wallets[i].address});
            balance.$promise.then(function(data) {
                $scope.totalBalance += parseFloat(data.balance);
                $scope.totalValueBtc = $scope.totalBalance * $scope.price;
            });
        }
    });
});

I need to calculate the aggregate value in BTC of the balances of all the dogecoin addresses from $scope.wallets. I handled the promises from the two api calls in a nested way, as you can see in the controller code.

on Jsfiddle

My question if there is a better way to do this data handling from multiple promises?

What if I have 5 promises to be resolved before data handling, each from different source? Do I need to place every one of them in the promise callback of the previous one?

Upvotes: 0

Views: 96

Answers (1)

cDecker32
cDecker32

Reputation: 811

I would suggest putting your logic into a function that can be called from anywhere to sum up the value of all wallets in the array.

Start by making the balance a part of the wallet object.

$scope.wallets = [
    { id: 0, type: 'doge', address: 'DT2rmMrutwzdZ8EXwzj4QFdcL6DtvGGkci', balance: {}},
    { id: 1, type: 'doge', address: 'DMoonjyH1aHLZc1kksmikBUhjXromn1ZN4', balance: {}}
];

Then you can do

$scope.getBalance = function () {
var tempBalanace = 0;
angular.forEach($scope.wallets, function (value, key) {
    tempBalance += value.balance * $scope.price;
});
$scope.totalBalance = tempBalance;
};

So now you can call $scope.getBalance() from all of your promises and the total balance will be updated accordingly. You may need to add some extra logic to handle a scenario where the balance or price is null (still awaiting a response), but whenever ANY record gets updated this will force an update of the overall balance with the last received values.

Upvotes: 1

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