generics.swift

/// Both objects will have a shared set of features to be used in the generic function
protocol HasSomeSharedFeatures {
    func performSharedThing()
}

/// Extends the base class with some shared features
class PFObject: NSObject, HasSomeSharedFeatures {
    func performSharedThing() { }
}

// Swift 4.1 - 5 ?
// extension Dictionary: HasSomeSharedFeatures where Key == String, Value: Any { }

// Adds overhead, but wraps a typed dict with a protocol
struct SupportingDict: HasSomeSharedFeatures {
    let dict: [AnyHashable: Any]
    func performSharedThing() {  }
}

// Array yay
typealias ArrayOfPFObjects = [PFObject]
typealias ArrayOfSupportingDicts = [SupportingDict]



let pfobjects: ArrayOfPFObjects = []
let arrObjects: ArrayOfSupportingDicts = []

/// Generic function
///
/// - Parameter input: Takes an input with the function constraint as
/// - Returns: Something out after processing
func doSomething<T: HasSomeSharedFeatures>(input: [T]) -> Any? {

    // Do your job here
    input.forEach {
        $0.performSharedThing()
    }

    return nil
}

func execute() {
    _ = doSomething(input: pfobjects)
    _ = doSomething(input: arrObjects)
}