CODEWITHSUNDEEP
objective-cswiftprotocolsobjective-c-blocks
Madu
Madu

Reputation: 5019

Protocol syntax inside block in swift

I have a method which accepts a block, the method signatures in objective C are

- (void) startWithFinishingBlock:(FinishingBlock _Nonnull)finishingBlock;

I have typedef FinishingBlock as below

typedef void (^FinishingBlock)(id<Operation> _Nonnull operation);

Now i am trying to call this methods from swift and having some trouble in writing it in swift. I am ending up with something like this.

    operation?.start(finishing: ({(operation : AnyObject) in

        } as? FinishingBlock)!)

But i know that it should not be AnyObject, i want here some object which conforms to <Operation> protocol. How i can define this in swift.

One additional thing that i have one Operation class and one <Operation> protocol in my code. So basically Operation class is conforming <Operation> protocol

Upvotes: 1

Views: 253

Answers (1)

Rob
Rob

Reputation: 437552

Whenever you're unsure, you can just infer the correct types, e.g.:

operation?.start { operation in
    // ...
}

Just for the sake of completeness, the syntax (neither employing the above trailing closure syntax nor inferring the type) would be:

operation?.start(finishing: { (operation: MyApp.Operation) -> Void in
    // ...
})

Because your Operation protocol clashes with the Foundation Operation type (i.e. the new name for NSOperation in Swift 3), you have to qualify your protocol name with your target name (MyApp in my example above). This is the advantage of inferring the type of the parameter, as you don't have to deal with this.

Regardless, if you have the opportunity, I might recommend renaming your Operation protocol to avoid any confusion in the future.

Upvotes: 1

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