Swift syntax for block with completionHandler... in delegate method

Question

This is a wrinkle on the regular NSURLSession completion block problem, which I'm having a heck of a time resolving into Swift syntax. The method is the authentication delegate callback, which is invoked on auth challenge; the developer calls the completion block with NSURLCredential, NSError.

The Objective-C method looks like this:

-(void) provideUsernamePasswordForAuthChallenge:(NSURLAuthenticationChallenge *)authChallenge completionHandler:(void (^)(NSURLCredential *, NSError *))completionHandler{

    NSURLCredential* credential = [NSURLCredential credentialWithUser:@"myname" 
                                                             password:@"mypass" 
                                                          persistence:NSURLCredentialPersistenceForSession];
    completionHandler(credential, nil);
}

The closest I think I've gotten in Swift, is this:

func provideUsernamePasswordForAuthChallenge(authChallenge: NSURLAuthenticationChallenge!,  completionHandler:(() -> (NSURLCredential?, NSError?)) {

    var cred = NSURLCredential(user: "myname", password: "mypass", persistence: NSURLCredentialPersistence.ForSession)
    return (cred, nil)
})

But, it's still barfing. Any recommendations?

what error are you getting?

Connor
– Connor

2014-06-19 01:35:29 +00:00
Commented Jun 19, 2014 at 1:35 — Connor
– Connor, Commented Jun 19, 2014 at 1:35

Lou Franco · Accepted Answer · 2014-06-19 01:41:11Z

15

a void function is (Type1, Type2)->()
you need to add the ->() for the method itself

You need to call completionHandler with (cred, nil), not return a tuple

func provideUsernamePasswordForAuthChallenge(authChallenge: NSURLAuthenticationChallenge!,  completionHandler:(NSURLCredential?, NSError?)->()) ->() {

   var cred = 
      NSURLCredential(user: "myname", password: "mypass", 
         persistence: NSURLCredentialPersistence.ForSession)
   completionHandler(cred, nil)
}

answered Jun 19, 2014 at 1:41

Lou Franco

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1 Comment

fqdn Over a year ago

This could be cleaned up even a little bit more: (1) the method itself doesn't need a return type since it is Void (so you can leave off the -> () in the method signature), and (2) since for NSURLCredential the type of the persistence argument is known, you can just provide the option that you want to use, .ForSession

Prakash Raj · Accepted Answer · 2014-09-30 06:12:46Z

1

This code may help ->

 AFAppDotNetAPIClient.sharedClient().GET("User", parameters:nil, success:{ (task : NSURLSessionDataTask!, JSON: AnyObject!) in
        // within block....

        }, failure:nil)

answered Sep 30, 2014 at 6:12

Prakash Raj

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Comments

Chuck · Accepted Answer · 2014-06-19 01:40:24Z

0

Your type is backwards — you want the completion handler to take two arguments and return none, but you've defined it as a function that takes no arguments and returns a pair. Flop the two sides of the arrow.

answered Jun 19, 2014 at 1:40

Chuck

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