Kuidas luua nõrk link protokolli olevale väljale?

You can use the keywords weak or unowned before declaring a protocol type field.

protocol MyProtocol: AnyObject { // Protocol must be limited to classes
    func doSomething()
}

class MyClass {
    weak var delegate: MyProtocol? // Weak reference to a field of type MyProtocol
    unowned var helper: MyProtocol // Unowned reference to a field of type MyProtocol (if you are sure the object always exists)
}

It is important to note that the protocol must be limited to classes (: AnyObject) to be able to use weak or unowned references. This guarantees that the type implementing the protocol is a reference type, not a value type.

For a protocol type field, weak is applied when the object referenced by the field can be released before the object containing this reference. If the referenced object is released, the field automatically becomes nil.

unowned is used when you are sure that the object referenced by the field always has the same or a longer lifecycle than the object containing this reference. The use of unowned is safe only if you guarantee the absence of cyclic references and are sure that the referenced object is always valid. If the object is released and you try to access it via an unowned reference, a crash will occur.

In most cases, weak is used for delegates and other similar patterns.