generics - Set of weak observers in Swift -

i trying implement structure allows me store set of weak observers.

here observer wrapper:

public func ==<t: hashable>(lhs: weakobserver<t>, rhs: weakobserver<t>) -> bool {   return lhs.hashvalue == rhs.hashvalue }  public struct weakobserver<t t: anyobject, t: hashable> : hashable {    private weak var weakobserver : t?    public init(weakobserver: t){     self.weakobserver = weakobserver   }    public var hashvalue : int {     return self.weakobserver!.hashvalue   }  } 

and here protocol every observer needs conform to:

public protocol datamodelobserverprotocol : class, hashable, anyobject {    func somefunc()  } 

usage:

public class datamodel: nsobject, datamodelinterface {    public var observers = set<weakobserver<datamodelobserverprotocol>>()   //^^^^^ using 'datamodelobserverprotocol' concrete type conforming protocol 'anyobject' not supported } 

now, while aware might limitation swift itself, looking alternative solution without having concrete class type constraint (if that's not possible, afraid case, i'd still love alternative "non-hacky" solutions).

using set hold references runs risk set need reference element using hashvalue and, when weak reference goes nil, hashvalue function crash.

i couldn't protocols found way similar functionality using generic function returns tuple of functions.

struct weakreference<t> {     weak var _reference:anyobject?     init(_ object:t) {_reference = object as? anyobject}     var reference:t? { return _reference as? t } }  func weakreferences<t>(_:t.type) -> (                                       getobjects: ()->[t],                                      addobject:  (t)->()                                     ) {      var references : [weakreference<t>] = []     func getobjects() -> [t]    {        return references.filter({ $0.reference != nil }).map({$0.reference!})     }     func addobject(object:t)    {        if getobjects().contains({ ($0 as! anyobject) === (object as! anyobject) })        { return }       references.append(weakreference(object))     }     return (getobjects:getobjects, addobject:addobject)    }  public protocol datamodelobserverprotocol: class, anyobject {    func somefunc() -> string }  public class datamodel: nsobject, datamodelinterface   {    var observers = weakreferences(datamodelobserverprotocol) } 

to add observers, use:

observers.addobject( yourobserver ) 

to iterate through observers :

for observer in observers.objects() {    observer.somefunc() } 

both functions type safe , accept/return datamodelobserverprotocol compliant objects