Creating Weak Protocol References in Pure Swift (Without @objc)

This tutorial will guide you through the process of declaring and using a weak protocol reference in a pure Swift environment.

In Swift, when working with protocols, especially in the context of delegates, it’s essential to manage references properly to avoid strong reference cycles. The official way to create a weak reference in Swift is by declaring the protocol as AnyObject.

Step 1: Declare the Protocol

First, define your protocol by inheriting from AnyObject. This marks the protocol as being exclusive to class types, allowing you to later declare weak references to instances conforming to this protocol.

protocol MyProtocolDelegate: AnyObject {
    // Protocol requirements go here
}

Here, MyProtocolDelegate is a protocol that only classes can adopt. This is achieved by using AnyObject in the protocol declaration.

Step 2: Implement the Class

Next, create a class that will have a weak reference to an instance conforming to the protocol.

class MyClass {
    weak var delegate: MyProtocolDelegate?
    // Other class properties and methods go here
}

In this example, MyClass has a property named delegate with a weak reference to an instance conforming to MyProtocolDelegate.

Step 3: Utilize the Weak Reference

Now, you can use the weak reference to communicate with the delegate without creating strong reference cycles.

class AnotherClass: MyProtocolDelegate {
    // Implement protocol requirements here
}

let myClassInstance = MyClass()
let anotherClassInstance = AnotherClass()

myClassInstance.delegate = anotherClassInstance

// Now, myClassInstance can interact with anotherClassInstance through the weak delegate reference.

By setting the delegate property of myClassInstance to an instance of AnotherClass (which conforms to MyProtocolDelegate), you establish a weak reference. This allows communication between the two instances without causing strong reference cycles.

Recap and Further Study

• Use AnyObject: When creating a protocol for delegates, mark it as AnyObject to ensure it can only be adopted by class types, allowing for the use of weak references.
• Understanding Weak References: Weak references are crucial for preventing strong reference cycles, especially when dealing with class instances.
• Delegates and Weak References: Delegates should often be marked as weak, especially when a child class communicates with its parent or when two non-hierarchical classes need to reference each other.
• Further Study: Delve into related concepts such as the unowned keyword and strong reference cycles, and consider reading additional articles for a more in-depth understanding.

By following these steps and guidelines, you can create a weak protocol reference in a pure Swift environment, ensuring proper memory management and avoiding retain cycles.