Passing dictionary objects to Objective C protocol in Swift

Question

I'm trying to pass a dictionary object to an Objective C protocol using swift.

the protocol code snippet is as follows:

@protocol MessageDelegate

- (void)handleNewMessageArrived:(NSDictionary *)messageContent;

@end

and this is the swift class the implements the protocol:

class ViewController: UIViewController, MessageDelegate
{
 ...

 func handleNewMessageArrived(messageContent : NSDictionary!)
 {
  ...    
 }
}

But the build fails, and the error I get is:

"the type 'ViewController' does not conform to protocol 'MessageDelegate"

I looked at this SO Question but it deals with a specific object type.

is there an error in the way I declare\implement the delegate method? or in the way I assume the arguments are mapped in swift?

I'm new to Swift so any Help will be much appreciated.

sbooth · Accepted Answer · 2015-03-18 10:35:01Z

7

Try implementing the method in your Swift class like this:

func handleNewMessageArrived(messageContent: [NSObject : AnyObject]!) {
    // Handle the message
}

answered Mar 18, 2015 at 10:35

sbooth

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4 Comments

Duncan C Over a year ago

@sbooth I haven't spent much time with Swift. Can you explain why you have to make the messageContent parameter an anonymous pointer in Swift? It's not id type (the equivalent) in Objective-C.

sbooth Over a year ago

@DuncanC The messageContent parameter is an implicitly unwrapped optional containing a Swift dictionary with NSObject keys and AnyObject values. This corresponds closely to NSDictionary and is the result of Swift's automatic bridging.

Duncan C Over a year ago

So by default container objects like dictionaries are containers of a specific type (e.g. dictionary of strings?) Isn't an NSDictionary a concrete type, and a valid parameter in Swift though?

sbooth Over a year ago

All Swift containers are type-safe (a good thing). NSDictionary is also a valid type in Swift, but the Swift <-> Objective-C bridge converts the types automatically.

beretis · Accepted Answer · 2017-10-19 12:09:16Z

1

In case of Swift 3, this is what you will need

func handleNewMessageArrived(messageContent: [AnyHashable : Any]!) {
    // Handle the message
}

answered Oct 19, 2017 at 12:09

beretis

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