SwiftData: Accessing a context outside of a view not possible.

Question

Created Sep ’23

Replies 4

Boosts 2

Views 1.9k

Participants 5

Getting a warning from the Xcode compiler about accessing a context outside of a view. It popped up in white text on a purple background, not the usual white on yellow warning color.

The actual warning text is: Accessing Environment<ModelContext>'s value outside of being installed on a View. This will always read the default value and will not update.

This seems to mean that any datastore access must be done within a view, and isn't possible from the model or some sort of DataManager class. Am I reading this correctly? I'm trying to keep the business logic out of the views. I can do it with everything except the datastore code because of this context issue. Doesn't seem to make sense.

Suggestions greatly appreciated.

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Answer 1

nojkepop OP

Oct ’23

I am running into this same problem. Did you ever resolve this?

0

Answer 2

Claude31 OP

Oct ’23

I hope this will help or at least provide hints: https://www.hackingwithswift.com/forums/swift/trying-to-access-managed-object-context-through-a-model/23266

0

Answer 3

724QD58FHA OP

Oct ’23

Receiving the same warning with:

import SwiftData

@MainActor class…: ObservableObject {
@Environment(\.modelContext) private var modelContext
init() {
let descriptor = FetchDescriptor<Location>(predicate: #Predicate {$0.areaName != ""})
let count = (try? modelContext.fetchCount(descriptor)) ?? 0 <<== Warning here
}}

Then the App Crashes

Not interested in a View with a List
Just a [fetchCount]

0

Answer 4

rily OP

6d

You can't access from outside a View, so create the modelContext in a view and give it along

Example:

struct HomeView: View {
  @Environment(\.modelContext) private var modelContext
  @Environment(\.dismiss) var dismiss
  @State private var dataModel: DataModel? // This is a class to control logic
...
  var body: some View {
    Button {
      dataModel = DataModel(modelContext: modelContext)
    } label: {
      Text("Go to DataModelUsingView")
    }
    .fullScreenCover(item: $dataModel) { dataModel in
      DataModelUsingView(DataModel: dataModel)
    }

class DataModelUsingView: ObservableObject, Identifiable {
  let modelContext: ModelContext

...

  init(modelContext: ModelContext) {
    self.modelContext = modelContext
  }

...

  func editModelContext() {
      modelContext.insert(stuff)
  }

}

struct DataModelUsingView: View {
  @StateObject var dataModel: DataModel

  var body: some View {
    Button {
      dataModel.editModelContext()
    } label: {
      Text("Edit Data")
    }
  }
}

something like this, use at your own risk

0