Sequencing asynchronous functions in Angular: Ensuring one function runs before another

When working with a save function that requires you to call another function to retrieve the revision number and make an API call, both of which are asynchronous in nature, how can you ensure one function waits for the other to execute?

$scope.getRevision = function(callback){
    Api.Product.querymyProdById({ prodId: $scope.editProdId }).$promise.then(function(result) {
        if (result && result.length >= 1 && result[0].effectiveDate != $scope.editProdmyDate) {
            $scope.editProdRevision = result && result[0].revision + 1;
            callback();
        } else {
            $scope.editProdRevision = 100;
        }
    });
}

$scope.saveProd = function(){
     $scope.getRevision(function(){});

     Api.Product.save({
        id: $scope.ProdId;
        revision:$scope.editProdRevision
         -some code

}

In the above code, I want to ensure that the save API is not called until the prodRevision is obtained.

Do you have any suggestions on how to achieve this?

javascriptangularjs

Answer №1

If you already have promises in place, avoid messing with callbacks. It's better to have your functions return a promise and utilize the then method for chaining calls.

$scope.fetchData = function(){
    return Api.Data.retrieveInfo(..).$promise...;
}

$scope.updateData = function() {
   return $scope.fetchData().then(function() {
        return Api.Data.update(...);
   })
}

Answer №2

Callbacks were created by the javascript deities for this specific purpose

$scope.saveProduct = function(){
     $scope.retrieveRevision(function(){
        // this section executes after the retrieval of the revision
        Api.Product.save({
           id: $scope.productId;
           revision:$scope.editProdRev
            -some code
        });
     });

}

Answer №3

An effective way to handle multiple async calls is by chaining them one after the other. Here's an example:

// Initial asynchronous GET request:
$http({
  method: 'GET',
  url: '/firstUrl'
})
.then(function successCallback(response) {
  // Callback for first request
  // Second async GET request:
   $http({
     method: 'GET',
     url: '/secondUrl'
   })
   .then(function successCallback(response) {

   }, function errorCallback(response) {

   });
}, function errorCallback(response) {
  // Error callback when first request fails
});

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