I want to store objects in an array, where objects are weak, and conforms to a protocol. But when I try to loop it, I get a compiler error:
public class Weak<T: AnyObject> {
public weak var value : T?
public init (value: T) {
self.value = value
}
}
public protocol ClassWithReloadFRC: class {
func reloadFRC()
}
public var objectWithReloadFRC = [Weak<ClassWithReloadFRC>]()
for owrfrc in objectWithReloadFRC {
//If I comment this line here, it will able to compile.
//if not I get error see below
owrfrc.value!.reloadFRC()
}
Any idea what the heck?
Bitcast requires types of same width %.asSubstituted = bitcast i64 %35 to i128, !dbg !5442 LLVM ERROR: Broken function found, compilation aborted!
I think there is a compiler limitation/bug. If you mark your protocol as @objc it will work, eg:
// Array of weak references of a protocol OK so long as protocol marked @objc
struct WeakReference<T: AnyObject> {
weak var value: T?
}
@objc protocol P { // Note @objc, class or AnyObject won't work
var i: Int { get }
}
class CP: P {
var i: Int = 0
}
let cP = CP() // Strong reference to prevent collection
let weakPs: [WeakReference<P>] = [WeakReference(value: cP)] // Note typed as `[WeakReference<P>]`
print("P: \(weakPs[0].value!.i)") // 0
It is annoying that you have to use @objc and therefore not a pure Swift solution, but since I am on iOS not a problem for me.
Generics don't do protocol inheritance of their resolving type in the way that you seem to imagine. Your Weak<ClassWithReloadFRC>
type is going to be generally useless. For example, you can't make one, let alone load up an array of them.
class Thing : ClassWithReloadFRC {
func reloadFRC(){}
}
let weaky = Weak(value:Thing()) // so far so good; it's a Weak<Thing>
let weaky2 = weaky as Weak<ClassWithReloadFRC> // compile error
I think the thing to ask yourself is what you are really trying to do. For example, if you are after an array of weakly referenced objects, there are built-in Cocoa ways to do that.
I was seeing a similar compiler error in Xcode 6.4. I needed an array of weak protocols to store multiple delegates for a view controller. Based on an answer to a similar question I found, I used a NSHashtable instead of a swift array.
private var _delegates = NSHashTable.weakObjectsHashTable()
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