javascript - 如何在parse.com的异步方法中使用for循环

Question

我想在for循环中调用parse.com的函数，但是当我将函数放入for循环中时，for循环就完成了，而函数没有响应。

for (var i = 0; i <tourPackage.length; i++) { 
        var Apackage = tourPackage[i].attributes;  
        tourPackageDest.set("package_id",tourPackage[i].id);
       tourPackageDest.set("itinerary",Apackage.holiday_short_detail);
        var SD = Apackage.destination.split(',');
            for(var k=0; k<SD.length;k++){
                var destPlace =                           Parse.Object.extend("Cities_World");//DestinationMaster
                 var query = new Parse.Query(destPlace);
                query.equalTo("place_name", SD[k]);
                query.find().then(function(results){
                    console.log(results);
                });
                tourPackageDest.save(null,{
                    success: function(Tpackage){
                        console.log("Successfully saved in PackageItineraryMaster");
                        }
                });
            }

}

Answer 1

您调用的许多方法(例如，.find()、.save())都是异步的。从表面上看，您正在编写代码，就好像它们是同步方法一样。以下是如何构建代码以解决这种异步性的示例 ( via the Parse docs ):

var query = new Parse.Query("Comments");
query.equalTo("post", 123);

query.find().then(function(results) {
  // Collect one promise for each delete into an array.
  var promises = [];
  _.each(results, function(result) {
    // Start this delete immediately and add its promise to the list.
    promises.push(result.destroy());
  });
  // Return a new promise that is resolved when all of the deletes are finished.
  return Parse.Promise.when(promises);

}).then(function() {
  // Every comment was deleted.
});

基本上，您希望将异步函数中的每个 promise 添加到一个数组中，并创建一个新的 promise ，当所有这些 promise 都得到解决时，该新的 promise 就会得到解决。