Firestore: Issue with data type of map value in the firestore document

[weinamdev]

Hi,

As I working with firestore plugin for the MAUI project, I encountered some issues dealing with the map within the document.

I did a testing of a simple document with map fields as below

For the common data type as the map value I am using (string, number, boolean and DateTimeOffset), I have no issue to create a class which implements IFirestoreObject and set them to cloud Firestore on Android platform.

        public class DataClassWithMaps : IFirestoreObject
        {
            [FirestoreProperty(nameof(StringMaps))]
            public Dictionary<string, string> StringMaps { get; set; } = new Dictionary<string, string>();

            [FirestoreProperty(nameof(NumberMaps))]
            public Dictionary<string, double> NumberMaps { get; set; } = new Dictionary<string, double>();

            [FirestoreProperty(nameof(BooleanMaps))]
            public Dictionary<string, bool> BooleanMaps { get; set; } = new Dictionary<string, bool>();

            [FirestoreProperty(nameof(DateMaps))]
            public Dictionary<string, DateTimeOffset> DateMaps { get; set; } = new Dictionary<string, DateTimeOffset>();
        }

However on Android, I encounter issue getting/retrieving the data.

No exception when calling doc.GetDocumentSnapshotAsync(), however exception occurred when attempt to access IDocumentSnapshot.Data when the class contains Dictionary<string, DateTimeOffset> OR Dictionary<string, bool> property, with the exception below

System.ArgumentException: 'Could not convert object of type Java.Lang.Boolean to Java.Lang.Object. Does it extend IFirestoreObject?'
System.ArgumentException: 'Could not convert object of type Firebase.Timestamp to Java.Lang.Object. Does it extend IFirestoreObject?'

On iOS, the condition is kind of different.
Exception happen on iOS by just calling doc.SetDataAsync to store the data to the cloud Firestore if Dictionary<string, DateTimeOffset> contain data in the class.

Exception has occurred: CLR/System.ArgumentException
An unhandled exception of type 'System.ArgumentException' occurred in Microsoft.iOS.dll: 'Couldn't put object of type System.DateTimeOffset into NSDictionary'
  at ObjCRuntime.Runtime.ThrowException(IntPtr gchandle)
   at UIKit.UIApplication.UIApplicationMain(Int32 argc, String[] argv, IntPtr principalClassName, IntPtr delegateClassName)
   at UIKit.UIApplication.Main(String[] args, Type principalClass, Type delegateClass)

However, unlike Android. iOS platform has no issue getting the document with these maps.

In summary,
Android has no issue set the document
iOS has no issue get the document
Android cannot get the document (.Data) if the document contains Dictionary<string, bool> OR Dictionary<string, DateTimeOffset>
iOS cannot set the document if the document contains Dictionary<string, DateTimeOffset>

Below is the sample code for further testing and investigation, may comment out part of the code to test the behavior.

Thank you.

  async Task ExcuteTestGetDataWithMap()
  {
      var db = CrossFirebaseFirestore.Current;
      DateTimeOffset dt = DateTimeOffset.Now;

      var doc = db.GetCollection("zzz").GetDocument("docWithMaps");

      var data = new DataClassWithMaps();       
      data.StringMaps.Add("Key1", "Hello World");  // both working
      data.StringMaps.Add("Key2", "Hello Universe"); 
      data.NumberMaps.Add("Key1", 999.99);  // both working
      data.NumberMaps.Add("Key2", -999.99); 
      data.BooleanMaps.Add("Key1", true); // Android can set cannot get, iOS Working
      data.BooleanMaps.Add("Key2", false); 
      data.DateMaps.Add("Key1", dt);  // Android can set cannot get, iOS cannot set can get
      data.DateMaps.Add("Key2", DateTimeOffset.Now); 
      await doc.SetDataAsync(data, SetOptions.Merge());

      var snapshot = await doc.GetDocumentSnapshotAsync<DataClassWithMaps>();
      if (snapshot?.Data != null)
      {
          var dataOutput = snapshot.Data;
          
          if (dataOutput.StringMaps.TryGetValue("Key1", out string? stringValue))
              Debug.WriteLine(stringValue ?? "");

          if (dataOutput.NumberMaps.TryGetValue("Key1", out double numberValue))
              Debug.WriteLine(numberValue);

          if (dataOutput.BooleanMaps.TryGetValue("Key1", out bool booleanValue))
              Debug.WriteLine(booleanValue);

          if (dataOutput.DateMaps.TryGetValue("Key1", out DateTimeOffset dtoValue))
              Debug.WriteLine(dtoValue.ToString());
      }
  }

[Cellus250]

I am also running into the same behavior with reads on Android originating from properties of type <string, object>.

[weinamdev]

Thanks @Cellus250 for providing the idea of using property Dictionary<string,object>

I did a modified test using Dictionary<string,object>, I am not sure the plugin supports non-strong type dictionary values (object), it somehow works beyond my expectation, however the outcome is unpredictable.

For DateTimeOffset as stored map value using Dictionary<string,object>, it behaves exactly the same as using Dictionary<string,DateTimeOffset>.
On Android, the data can set, but encounter exception when attempt to access the Snapshot.Data
On iOS, exception happen when attempt to set, however if the data already exist on cloud firestore, it has no issue retrieving the value with the property of Dictionary<string,object>

For boolean value, I can set them on both platforms. But unlike using Dictionary<string,bool> which has the exception, I can retrieve (get) data on Android using Dictionary<string,object>

One very critical issue of using Dictionary<string,object> on iOS, the plugin only able to retrieve string and DateTimeOffset value, while failing to get numbers (long or double) and boolean. It just has “null” value of the map values are the types above, so basically unusable unless you just limit the usage of Dictionary<string,object> for string value, so basically just better using Dictionary<string,string> for certain outcome.

The sample code as below

    public class DataClassWithObjectMap : IFirestoreObject
        {
            // Not working on android as the plugin support long (Int64) instead of int (Int32)
            //[FirestoreProperty(nameof(IntegertMap))]
            //public Dictionary<string, int> IntegertMap { get; set; } = new Dictionary<string, int>();

            [FirestoreProperty(nameof(LongMap))]
            public Dictionary<string, long> LongMap { get; set; } = new Dictionary<string, long>();

            [FirestoreProperty(nameof(ObjectMap))]
            public Dictionary<string, object> ObjectMap { get; set; } = new Dictionary<string, object>();
        }

   async Task Exceute_FireStore_319()
   {
       var db = CrossFirebaseFirestore.Current;
       var doc = db.GetCollection("zzz").GetDocument("docWithObjectMap");

       var data = new DataClassWithObjectMap();
    
       data.ObjectMap.Add("Key1", 999);
       data.ObjectMap.Add("Key2", 999.99);
       data.ObjectMap.Add("Key3", "Hello World");
       data.ObjectMap.Add("Key4", false);
       data.ObjectMap.Add("Key5", FieldValue.IntegerIncrement(1)); // android can set, iOS cannot set
       data.ObjectMap.Add("Key6", DateTimeOffset.Now); // android can set cannot get, iOS cannot set can get

       data.LongMap.Add("Key1", 999);
       await doc.SetDataAsync(data, SetOptions.Merge());

       var snapshot = await doc.GetDocumentSnapshotAsync<DataClassWithObjectMap>();
       if (snapshot?.Data != null)
       {
           var dataOutput = snapshot.Data;

           if (dataOutput.ObjectMap.TryGetValue("Key1", out object? value1))
               Debug.WriteLine(value1 ?? "");

           if (dataOutput.ObjectMap.TryGetValue("Key2", out object? value2))
               Debug.WriteLine(value2 ?? "");

           if (dataOutput.ObjectMap.TryGetValue("Key3", out object? value3))
               Debug.WriteLine(value3 ?? "");

           if (dataOutput.ObjectMap.TryGetValue("Key4", out object? value4))
               Debug.WriteLine(value4 ?? "");

           if (dataOutput.ObjectMap.TryGetValue("Key5", out object? value5))
               Debug.WriteLine(value5 ?? "");

           if (dataOutput.ObjectMap.TryGetValue("Key6", out object? value6))
               Debug.WriteLine(value6 ?? "");

           if (dataOutput.LongMap.TryGetValue("Key1", out long numericvalue1))
               Debug.WriteLine(numericvalue1);
       }
   }

So I doubt Dictionary<string,object> is really supported/workable for this plugin, perhaps @AdamEssenmacher can help to answer.

Unlike iOS can only work with string and Timestamp, I can retrieve the map values of boolean and number using Dictionary<string,object> on Android using the code above, other than Timestamp (exception happen as like using Dictionary<string,DateTimeOffset>)