在指针列分析查询 [英] Parse query on pointer column

问题描述

我已经种问到这个问题，但我会尽量在成为一个更清晰一点，希望更加具体。

I've already kind of asked this question, but i'm going to try to be more specific in the hope of being a little clearer.

我有一个xamarin Android项目，使用Parse.com作为后端。我有两个表（或类），其中一个包含的信标的列表（称为信标），和一种含有一个类别列表（称为BeaconCat）。表中的信标类的标题是这样的：

I have a xamarin Android project, using Parse.com as the back end. I have two tables (or classes), one which contains a list of beacons (called Beacons), and one which contains a list of categories (called BeaconCat). The headings of the table for the beacons class looks like:

ObjectID   |  minor  | major  |  CatID (this is the 'pointer' column to BeaconCat)
111111     |  200     |  999  |   12345

在BeaconCat类的标题是这样的：

The headings of the BeaconCat class looks like:

   ObjectID  |  Category
    12345    |   Sports

所有我想要做的，是运行在传递一个次要号，该号码被第一个表抬头，并返回第二个表类别列的值的查询。

All i'm trying to do, is run a query that passes in a 'minor' number, that number gets looked up in the first table, and returns the value of the category column in the second table.

所以在上面的例子中，我想在200次传球，并取回字符串'运动'。

So in the example above, i want to pass in the minor of 200, and get back the string 'sports'.

好像应该很容易，但我真的很挣扎。

Seems like it should be very easy but i'm really struggling.

我一直在尝试以下的变化：

I've been trying variations of the following:

public async void getBeaconCat(Int32 minor)
  {
    try{

            var innerQuery = ParseObject.GetQuery("Beacons");
            innerQuery.WhereEqualTo("minor", minor);
            innerQuery.Include("CatID");

            var newQuery = ParseObject.GetQuery("BeaconCat");
            newQuery.WhereMatchesQuery("Category", innerQuery);

            IEnumerable<ParseObject> Myresults = await innerQuery.FindAsync();

            foreach (var result in Myresults)
             {

                var category = result.Get<string>("Category");
                Console.WriteLine ("Category is " + category);
             }

            }
                catch{
                    Console.WriteLine ("There was a problem fetching data from parse");
            }

        }

什么我尝试似乎只是直接去捕捉，而不是返回一个字符串值。

Anything i try just seems to go straight to the catch and not return a string value.

在这个AP preciated任何帮助。

Any help on this appreciated.

推荐答案

OK，终于得偿所愿。这工作：

OK, finally got it. This works:

public async Task getBeaconCat(Int32 minor)
        {
            try{


                var innerQuery = ParseObject.GetQuery("Beacons").WhereEqualTo("minor", minor).Include("CatID").Include("Category");

                IEnumerable<ParseObject> MyFirstResults = await innerQuery.FindAsync();
                foreach (var result in MyFirstResults)
                {
                    var catObject = result.Get<ParseObject>("CatID");

                    var category = catObject.Get<string>("Category");
                    Console.WriteLine ("The category is......... " + category);
                    return category;

                }

            }
            catch{
                Console.WriteLine ("There was a problem fetching data from parse");
            }

        }

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