How to handle multi-inheritance in Swift? - swift

Question

This is probably 2 swift questions in one...
How do I solve a situation where I want to extend an existing base class (UIView in my case) with functionality that requires stored properties? ...so that I can reuse the code for other classes?
I have tried to solve it through composition below, but I don't know if there is a more obvious way that I just can't see as I am fairly new to swift...
The second question:
In my implementation I have an abstract class ManagedComponentImpl which needs an eventReceiver object which is going to be the containing UIView subclass.
The problem I have with my implementation is that swift forces me to define an object binding where Receiver:NSObject for ManagedComponentImpl, so that I can declare the optional variable eventReceiver as weak. (and I guess I would create a memory leak otherwise). However I would want to use this implementation on a variety of objects (which could of course all inherit NSObject, but they do not actually need to for other reasons but this, so it seems odd). So question number 2: Is there a way to avoid this?
EDIT: And yes! I made a mistake mixing model and view code here, but I guess the fundamental problem remains when you switch UIViewController for UIView :-)
public protocol ManagedConnection {
var connectionKey:String { get set }
}
public protocol ManagedComponent: ConnectionObserver {
var connectionKey:String { get set }
func connectTo()
func disconnectFrom()
}
public protocol EventReceiver: ConnectionObserver {
var variableSet:Set<VariableID>? { get }
var handleVariableUpdates: ((Set<VariableID>)->Void)? { get }
}
class ManagedComponentImpl<Receiver: EventReceiver> where Receiver:NSObject {
public var _connectionKey: String = Shared
//The connection Key
public var connectionKey: String
{
set {
disconnectFrom()
self._connectionKey = newValue
connectTo()
}
get {
return _connectionKey
}
}
// The varset needed by this control
weak var eventReceiver:Receiver!
// handler for the status pane variables
//
var connectionObserverHandlerID:UInt16 = 0
var eventHandlerID:UInt16 = 0
public init(receiver:Receiver) {
self.eventReceiver = receiver
}
public func connectTo() {
guard let manager = Connections.shared[self.connectionKey] else { return }
let connection = manager.connection
// disconnect any previous connections
disconnectFrom()
// Connect the connection observer
connectionObserverHandlerID = connection.addConnectionObserver(observer: eventReceiver)
if let variableSet = eventReceiver.variableSet, let handler = eventReceiver.handleVariableUpdates {
eventHandlerID = connection.requestVariables(variables: variableSet, handler: handler)
}
}
public func disconnectFrom(){
guard let manager = Connections.shared[self.connectionKey] else { return }
let connection = manager.connection
// Disconnect
if connectionObserverHandlerID != 0 {
connection.removeConnectionObserver(id: connectionObserverHandlerID)
}
if eventHandlerID != 0 {
connection.unRequestVariables(ident: eventHandlerID)
}
}
}
class ManagedUIView: UIView, ManagedComponent, EventReceiver {
private var component:ManagedComponentImpl<ManagedUIView>!
public var variableSet:Set<VariableID>?
public var handleVariableUpdates:((Set<VariableID>)->Void)?
public override init(frame: CGRect) {
super.init(frame: frame)
component = ManagedComponentImpl<ManagedUIView>(receiver: self)
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
component = ManagedComponentImpl<ManagedUIView>(receiver: self)
}
var connectionKey:String {
set {
component.connectionKey = newValue
}
get {
return component.connectionKey
}
}
func connectTo() {
component.connectTo()
}
func disconnectFrom() {
component.disconnectFrom()
}
func notifyState(state: ConnectionState) {}
}

Answer 1

Okay - for everybody reading this, the answers are:
- The problem should probably be solved by a delegate and not by inheritance.
- To avoid inheriting from NSObject: the problem seems to be that protocols can not only be implemented by classes. Therefore the protocol needs a class limitation to work as weak references. As a result ManagedComponentImpl does not need to be generic any more and I can just have a weak CAPEvent receiver optional.