firebase-ios-sdk: Firestore crashing with `FIRQueryDocumentSnapshot` and Swift's map function in SwiftUI canvas

Step 0: Are you in the right place?

Yes

[REQUIRED] Step 1: Describe your environment

Xcode version: 11.3.1 (11C504)
Firebase SDK version: 6.16.0
Firebase Component: Firestore
Component version: 1.10.0
Installation method: CocoaPods

[REQUIRED] Step 2: Describe the problem

Steps to reproduce:

If I would like to call map on a documents array from firestore, the SwiftUI canvas in Xcode crashes. Note that the same code works flawlessly if I run the app in the simulator. Only the canvas view is affected. With canvas I refer to the PreviewProvider feature in SwiftUI.

Please also note that https://github.com/firebase/firebase-ios-sdk/issues/4271 is somehow related - but in my case I don’t have multiple internal frameworks.

Crashlog:

Precondition failed: NSArray element failed to match the Swift Array Element type
Expected FIRQueryDocumentSnapshot but found FIRQueryDocumentSnapshot: file /BuildRoot/Library/Caches/com.apple.xbs/Sources/swiftlang/swiftlang-1100.2.280/swift/stdlib/public/core/ArrayBuffer.swift, line 354

Relevant Code:

        self.db.collectionGroup("Foo").addSnapshotListener { querySnapshot, err in
            guard let documents = querySnapshot?.documents else {
                return
            }
            let data = documents.map { Foo(document: $0) } // canvas crash
            [...]
        }

About this issue

Original URL
State: open
Created 4 years ago
Comments: 18 (9 by maintainers)

Most upvoted comments

I had the same problem with cocoapods umbrella frameworks and I solve problem with loop “for i in 0…<document.count” just read the code bellow

database.collection("<Your_Collection>").document("<Your_ID_DOC_IF_HAVE>").collection("<Your_ANOTHER_COLLECTION_IF_HAVE>").getDocuments()
{ [weak self] (snapshot,err) in
	guard let self = self else {return}
	if let error = err {
        print("Couldn't read sessionsDocument \(error)")
    } else {
        if (snapshot?.documents.count ?? 0) > 1 {
            let countDocs = snapshot!.documents.count
            for i in 0..<countDocs{
                print("DATA: \(snapshot!.documents[i].data())")
                let data = snapshot!.documents[i].data()
                // use data here
            }
        }else{
            // Error handler empty data
        }
    }
}

Maybe it’s not the better way but it works

DanielMoraCSG on Jun 26, 2020

Done. Thanks for the hint. I googled before to make sure it is okay to push (https://stackoverflow.com/a/44937513/4041516). I was uncomfortable though, and made the demo db at least readonly 😃 But now, even better - no GoogleService-Info.plist anymore! Of course you now have to setup your own db.

adriano-s on Jan 29, 2020

Thank you very much for doing that - can you please delete the project and re-upload it without a GoogleService-Info.plist? Just want to make sure it’s not easily accessible.

ryanwilson on Jan 29, 2020

Should be reproducible, but I’m going to create a minimum project that I can share.

adriano-s on Jan 29, 2020