CODEWITHSUNDEEP
swiftcore-dataswiftui
brownandrew15
brownandrew15

Reputation: 55

Initialising a variable in SwiftUi view from CoreData FetchRequest

I am relatively new to SwiftUI and would like to have a view where the user selects a result from a CoreData FetchRequest in a Picker. I have the following lines inside the view struct but outside the view body,

@FetchRequest(
    entity: Person.entity(),
        sortDescriptors: [
            NSSortDescriptor(keyPath: \Person.name, ascending: true)
        ]
) var people: FetchedResults<Person>
    
@State var currentPerson:Person

Inside the view body, I have got a Picker that saves the selected value to currentPerson but when I try to run the program in the simulator, I get an error that states Missing argument for parameter 'currentPerson' in call at the preview struct at the end of the file.

If I try to initialise currentPerson with the first item in people I get a error that states Cannot use instance member 'people' within property initializer; property initializers run before 'self' is available.

Apart from passing a Person object into the view, the other solution that I have had work is the create an object to initialise currentPerson variable is to create a Person object but not pass the Managed Object Context as the parameter.

However when I run the program it shows CoreData: error: Failed to call designated initializer on NSManagedObject class 'Person' in the console, but the program runs as intended.

Is this the best way to do this or am I missing something that would work better? Thanks!

Upvotes: 0

Views: 1291

Answers (1)

Helperbug
Helperbug

Reputation: 567

Use a computable property. That will not be called until after self is available. Then, as was said above, use an optional calculated property for the first person.

var people : [Person] {
    let fetchRequest = Person.fetchRequest()
    fetchRequest.sortDescriptors = [NSSortDescriptor(keyPath: \Person.name, ascending: true)]

    return fetchRequest.wrappedValue
}

var currentPerson : Person? {
    return people.first
}

Upvotes: 0

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