Firestore error ‘Requested Entity not found’ in swift app

I’m getting this error:

[Firebase/Firestore][I-FST000001] WriteStream (129e2dd38) Stream error: 'Not found: Requested entity was not found.'

in my app built on SwiftUI and i cannot seem to find any information relating to this error and firestore.

for context: this is an app for a dog walker, Dogs have a many-to-many relationship with Customers. this particular bit of code is supposed to add a list of DocumentID’s from the dogs collection

when a dog is added to Firestore, a Dog object is added to a Customer.dogs
and then this function is called, passing in the Customer in quesiton

func saveDogsTo(_ customer: Customer){
        let db = Firestore.firestore()
        print("saveing listed dogs to (customer.id)")
        var ids: [String] = [String]()
        for dog in customer.dogs{
            print("Appending id: (dog.id)")
            ids.append(dog.id!)
        }
        
        db.collection("customer").document(customer.id!).updateData(["dogs": ids])
    }

The print statements are showing the correct information, all the ID’s exist on Firestore (I’ve checked), and this is not down to dogs being missing from a customer’s document (only cause i could think of, but i tried running this code on documents with and without existing dogs fields)

I’m at a dead end here so can anybody see my mistake?

Happy to provide any extra information as required. Just ask 🙂

Thanks

For the benefit of anyone else with a similar error.

I was trying to update a document in the customer collection, however the collection was actually called customers meaning Firestore was looking in the wrong place for the document

Anybody else with this error should check all their collection references are spelled correctly -_-