Appending map object data inside an array within Firestore (Swift / iOS)

[haIIux]

I'm not sure the best method to ask this question but I'm going to go for it... I am building out an application which I am using Firestore for. The data is arranged as follows within the Firestore website interface and accepts without issue and also reads without issue, it's the writing that is the problem.

cozys:
      0: 
          name: String
          url: String
          tags: [String]?
          notes: String?
      1:
         name: String
         url: String
         tags: [String]?
         notes: String?

As you can see, cozys is an array and the objects within, are a Firestore map. I've tried a few methods to get this to work which you will find below.

/// This throws an error indicating that nested arrays are unsupported. I assumed that is because I'm trying to add the tags array. 
.setData(
    [
       "cozys": FieldValue.arrayUnion(
          [
             "name": name
             "url": url
             "tags": tags
             "notes": notes
          ]
    ]
)

/// This will just append the data in an array, not as a map object as I need and will not accept my array.
.setData(
    [
       "cozys": FieldValue.arrayUnion(
          [
             name
             url
              notes
          ]
    ]
)

I visited this link via the docs and attempted to do it that way as well which yielded the error below the code snippet.

        let appendData = Model(
            name: name,
//            tags: tags,
            url: url,
            notes: notes)

                    .setData(
                        [
                            "cozys": FieldValue.arrayUnion([appendData])
                        ], merge: true
                    )

*** Terminating app due to uncaught exception 'FIRInvalidArgumentException', reason: 'Unsupported type: __SwiftValue'
terminating with uncaught exception of type NSException

[morganchen12]

Hi @haIIux, it's not clear exactly what you want the database to look like after your write succeeds. Assuming cozys is a collection, you should be using

Firestore.firestore().collection("cozys").document("2").setData([
  "name": name,
  "url": url,
  "notes": notes
])

[haIIux]

Hello @morganchen12, thanks for the quick response. Please allow me to hopefully clear up the data model and associated information.

I have a collection of Releases which are comprised of the following model.

struct ReleaseModel: Identifiable, Codable, Hashable {
    @DocumentID var id: String?
    var name: String
    var date: String?
    var cozys: [CozyModel]?
}

The CozyModel is defined as follows.

struct CozyModel: Identifiable, Codable, Hashable {
    @DocumentID var id: String?
    var name: String
    var tags: [String]?
    var url: String
    var notes: String?
}

Within using the Firestore Web Interface (ie Firebase Console), I am able to create out this using the following idea...

Releases
  | -> Release Name
  | -> [Cozys]
        |
        | - [0] -> {
                          name: Cozy Name
                          url: Firebase Storage URL (Image)
                          notes: Cozy Notes
                          tags -> [
                             [0] - tag1
                             [1] - tag 2
                          ]
                       }
        | - [1] -> {
                          name: Cozy Name
                          url: Firebase Storage URL (Image)
                          notes: Cozy Notes
                          tags -> [
                             [0] - tag1
                             [1] - tag 2
                          ]
                       }

As you can hopefully tell, [Cozys] are an array type, comprised of map objects with a nested array tags. When I manually enter the data within the Firestore Console, I have no issues retriving the data with the below function however, I am unable to determine a method to write to them.

    func fetchReleases() {
        firestore.collection("collections")
            .addSnapshotListener { snapshot, error in
                guard let documents = snapshot?.documents else {
                    print("No documents found.")
                    return
                }
                self.collections = documents.compactMap { queryDocumentSnapshot -> ReleaseModel? in
                    return try? queryDocumentSnapshot.data(as: ReleaseModel.self)
                }
            }
    }
    ```
    
 

[morganchen12]

Got it, thanks. As you've seen you'll run into the nested arrays problem when trying to write tags. Have you considered making cozys a subcollection instead of an array?

[haIIux]

That would be the next approach however, I'm struggling with the implementation and logic due to my skill abilities. I was hoping to use Codable as the below method is nice and simple however, I'm unsure how to get the second sub-collection mapped properly within ReleaseModel.

self.collections = documents.compactMap { queryDocumentSnapshot -> ReleaseModel? in
return try? queryDocumentSnapshot.data(as: ReleaseModel.self)

[morganchen12]

Document reads in Firestore are shallow, so they don't include subcollection contents. This is to prevent accidentally fetching very large subcollections of documents. You'll need to use a separate query to fetch the subcollection documents, and then combine them with your ReleaseModel object in code.