CODEWITHSUNDEEP
swiftclassdelegatesprotocolssubclass
Chewie The Chorkie
Chewie The Chorkie

Reputation: 5234

How do you call a delegate's function on a subclass in Swift?

Class A is the delegate. Class B had a protocol with the methods, and I could call them simply by calling something like delegate?.myFunc()

protocol ClassBDelegate: class {
    func myFunc()
}

class Class B {
    weak var delegate: ClassBDelegate?
    delegate?.myFunc()
}

But now myFunc() is in a another class (Class C) that Class A uses, but now I want Class B to call a function in Class A's instance of Class C.

How is that done? I know there's an answer, but maybe I don't know what to search for? I wish I could write something like delegate?.classC.myFunc() but it won't let me do that.

Upvotes: 0

Views: 147

Answers (2)

Duncan C
Duncan C

Reputation: 131418

The whole point of a protocol is that it decouples you from having to specify a particular class that provides a service. Instead, you just specify that some object that conforms to the protocol provides the service.

You just need to make both your ClassA and ClassB objects have the same delegate. Then each one will call the delegate directly.

Upvotes: 1

matt
matt

Reputation: 535201

It's not class B's business to know anything about what its delegate does in order to fulfill its commands. That is the point of the protocol / delegate pattern. The protocol hides the implementation — more than that, the very identity — of the delegate.

It is class A, serving as the delegate, that will respond to myFunc by talking to its class C helper in some way. Maybe that is its delegate, I don't know. That doesn't matter. But don't change anything about class B's knowledge of the situation or the way it talks.

So, you need to write a function in class A that will call its class C for you. Class B should know nothing about what happens at the far end if class A is the delegate. That's a private implementation detail.

Upvotes: 2

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