Core Data generic fetch request [duplicate]

Question

I use following code to fetch data from Core Data entity One:

func fetchDataOne() {
let fetchRequest: NSFetchRequest<One> = One.fetchRequest()
    do {
        fetchRequest.predicate = NSPredicate(format: "questionWasShown == %@", NSNumber(value: false))
        // Save result to result array
        let result = try PersistentService.context.fetch(fetchRequest)

        if result.count > 0 {
             // do some stuff
            }
  }

I plan to add more entities(20-30). It will be difficult to maintain 30 different fetch requests. I want to rewrite this line

let fetchRequest: NSFetchRequest<One> = One.fetchRequest() 

so that i can use generic code. I want to achieve something like that

func fetchData(entity: T) {
 ...
 let fetchRequest: NSFetchRequest<T> = T.fetchRequest()
 ...
 }

It is possible in Core Data?

Answer 1

As Ryan said above in comments, you have to let the compiler know T has the method fetchRequest, like so:

func fetchData<T:NSManagedObject>(entity: T.Type) {
    let fetchRequest = T.fetchRequest()
    do {
        fetchRequest.predicate = NSPredicate(format: "questionWasShown == %@", NSNumber(value: false))
        let result = try CoreDataHelper.managedObjectContext.fetch(fetchRequest)
        if result.count > 0 {
            // do some stuff
        }
    } catch {

    }
}

Usage:

self.fetchData(entity: One.self)