如何在Swift中将类类型作为函数参数传递？

Question

How can i do the following code ?

    func setupFetchResultController<AnyNSManagedObject>(entityToFetch: AnyNSManagedObject) {
    let fetchRequest:NSFetchRequest<entityToFetch> = entityToFetch.fetchRequest()
}

it produce an error with error message:

Use of undeclared type 'entityToFetch'

also when i've tried the following code

    func setupFetchResultController<AnyNSManagedObject>(entityToFetch: AnyNSManagedObject) {
    let fetchRequest:NSFetchRequest<AnyNSManagedObject> = AnyNSManagedObject.fetchRequest()
}

it also produced an error with error message:

Type 'AnyNSManagedObject' does not conform to protocol 'NSFetchRequestResult'

Answer 1

Use generics

func setupFetchResultController<T: NSManagedObject>(entityToFetch: T) {
    let fetchRequest = T.fetchRequest()        
}

or

func setupFetchResultController<T: NSManagedObject>(entityToFetch: T) {
    let fetchRequest: NSFetchRequest<NSFetchRequestResult> = T.fetchRequest()
}