SwiftUI with Core Data: Fetch request with predicate crashes

Question

I have successfully added Core Data to my SwiftUI project. I need to filter the results by type. When I add a predicate to the fetch request the app crashes at the point where the view containing the fetch request tries to load.

The error is Thread 1: EXC_BAD_ACCESS (code=1, address=0x1)

 @Environment(\.managedObjectContext) var managedObjectContext
@FetchRequest(entity: Task.entity(),
    sortDescriptors:[
        NSSortDescriptor(keyPath: \Task.type, ascending: true),
        NSSortDescriptor(keyPath: \Task.totalScore, ascending: false),
    ],
        predicate: NSPredicate(format: "type == %@", Int16(1))) //this is the line that crashes the app
 var tasks: FetchedResults<Task>

If I change the Int16(1) to Int16(0), the app does not crash but no data appears in the list.

This is the first app I have witten using core data so I need help.

I suspect your problem is your predicate format. %@ expects a String or a value that Swift can implicitly convert to a String, so what placeholder would you use for an Int? — andrewbuilder
– andrewbuilder, Commented Sep 1, 2019 at 18:55

K. Law · Accepted Answer · 2019-09-01 20:07:51Z

4

Thanks to andrewbuilder. He got me looking in the right direction. The correct way to use a predicate that expects an Int is:

predicate: NSPredicate(format: "type == %i", Int16(1)))

I was using %@ when I should have used %i.

answered Sep 1, 2019 at 20:07

K. Law

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MacMark · Accepted Answer · 2019-11-22 10:00:34Z

1

You can also make the int an NSNumber object:

NSPredicate(format: "type == %@", @(1))

answered Nov 22, 2019 at 10:00

MacMark

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