CODEWITHSUNDEEP
objective-cswift
vivek
vivek

Reputation: 459

How to implement a swift delegate method in objective-C having parameter?

I have a swift protocol having following delegate method 

@objc public protocol CuteDelegate: NSObjectProtocol {
    @objc func myCuteFunc(name: NSString)
}

I have declared delegate object in swift as well

weak var delegate : CuteDelegate?

In my objective C controller where I am implementing the above delegate method is as follows

-(void)myCuteFunc:(NSString* )name{

}

But while calling the method in swift controller

 self.delegate?.myCuteFunc(name: str as NSString)

I get unrecognized selector sent to instance

Any clue what's the issue

Upvotes: 0

Views: 514

Answers (1)

vacawama
vacawama

Reputation: 154731

You need to account for the first arguments's name:

Either:

  1. Make your Objective-C function -(void)myCuteFuncWithName:(NSString* )name

Or:

  1. Change your protocol to @objc func myCuteFunc(_ name: NSString) and call it with self.delegate?.myCuteFunc(str)

This is just an artifact of the way Objective-C function names work vs. the way Swift names its arguments. Objective-C has no way of naming the first argument (which is usually described by the function name), so if Swift has a label for the first argument, the convention used is to add With plus the argument name (with the argument name capitalized) to the function name. By adding _, you make the first argument unnamed and that translates better to the Objective-C naming convention.

Upvotes: 3

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