Swift: How to determine object type based on the outcome of switch statement - swift

Question

I have a function that returns whether an item exists in 1 of 3 CoreData entities, depending on the list: CoreDataList enum argument passed to that function:
static func listContains(word: String, list: CoreDataList) -> Bool {
var reply = false
switch list {
case .itemsSearched:
let request : NSFetchRequest<ItemsSearched> = ItemsSearched.fetchRequest()
case .itemsAdded:
let request : NSFetchRequest<ItemsAdded> = ItemsAdded.fetchRequest()
case .itemsFinished:
let request : NSFetchRequest<ItemsFinished> = ItemsFinished.fetchRequest()
}
do {
request.predicate = NSPredicate(format: "item == %#", word)
let fetchedResults = try context.fetch(request)
if fetchedResults.count == 1 {
reply = true
}
} catch {
print ("fetch task failed", error)
}
return reply
}
The problem here is that let request cannot be initialized before the switch statement because its type will depend on the outcome of the switch.
Therefore I cannot find a way to do this function without repeating the entire do catch block for each case, which will result in repeating the same code three times. The other option is to separate into three different function, but this presents the same code repetition problem.

Answer 1

You can create a generic function for this
static func checkCount<T: NSManagedObject>(word: String, context: NSManagedObjectContext, type: T.Type) -> Bool {
let request = T.fetchRequest()
request.predicate = NSPredicate(format: "item == %#", word)
do {
let fetchedResults = try context.fetch(request)
if fetchedResults.count == 1 {
return true
}
} catch {
print ("fetch task failed", error)
}
return false
}
and then call it from inside the switch
case .itemsSearched:
return checkCount(word: word, context: context, type: ItemsSearched.self)
Note that I added context as a parameter to the function since I didn't know how it is declared, perhaps that parameter isn't needed.