Fetch core data entity in list

Question

The core data User I create with property id and name, which I want to fetch it into list.

struct MyView: View {
    @FetchRequest(entity: User.entity(), sortDescriptors: []) var users: FetchedResults<User>

    var body: some View {
        VStack {
            List {
                ForEach(users, id: \.id) { user in  // Type '_' has no member 'id'
                    // Text(user.name)
                }
            }
        }
    }
}

I'm confused with the error report seems it is not successfully import core data entity.

UPDATE

When I try to use the name property in list, it also report Value of type 'NSManagedObject' has no member 'name' error message.

ForEach(users, id: \.id) { user in
    Text(user.name)
}

Felix Marianayagam · Accepted Answer · 2020-03-12 08:52:12Z

2

At times, you need to build the project for the entity to be recognized in code. Here's the code for loading the CoreData entity User with id and name.

struct ContentView: View {
    @Environment(\.managedObjectContext) var context
    @FetchRequest(entity: User.entity(), sortDescriptors: [])
    var users: FetchedResults<User>

    var body: some View {
        List {
            ForEach(users, id: \.id) { user in
                Text("Id = \(user.id), Name = \(user.name ?? "")")
            }
        }
    }
}

Alternatively, you can make the User entity conform to Identifiable. Doing so, you can skip the id parameter in the ForEach.

extension User: Identifiable {
}

ForEach(users) { user in
    Text("Id = \(user.id), Name = \(user.name ?? "")")
}

edited Mar 12, 2020 at 8:52

answered Mar 12, 2020 at 5:16

Felix Marianayagam

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3 Comments

Felix Marianayagam Over a year ago

Which version of XCode are you using?

ccd Over a year ago

The version 11.3.1.

Felix Marianayagam Over a year ago

I'm using the same version and I don't see any errors. Are you sure you created name and id attributes with appropriate types for the User entity? I've updated the answer with a screenshot of my entity.

ccd · Accepted Answer · 2020-03-12 09:36:17Z

0

Referencing this article, I create a new UserRow struct to hold the core data entity, and it works correctly for me. But I think there is some knowledge I have missing in this situation, it will be very kind if someone could explain for me.

// in MyView add the new struct

struct UserRow: View {
    var user: User

    var body: some View {
        Text(user.name ?? "No name given")
    }
}


// then replace the list with

List {
    ForEach(users) { user in
        UserRow(user: user)
    }
}

answered Mar 12, 2020 at 9:36

ccd

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5 Comments

Felix Marianayagam Over a year ago

Please post this a new question. It this code works for you, what do you think you are missing?

ccd Over a year ago

I think about why we need to create a struct to reflect to core data entity, is it possible to use entity directly?

Felix Marianayagam Over a year ago

Which struct are you referring to? Where do you want to use entity directly?

ccd Over a year ago

The struct var user: User must be create to hold the var users: FetchedResults<User>.

Felix Marianayagam Over a year ago

I don't seem to understand your question.

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