CODEWITHSUNDEEP
iosswift
momentsnapper
momentsnapper

Reputation: 605

How to cast from AnyObject to the dynamic type?

I have a scenario where I've to cast an AnyObject to a dynamic type (available only at runtime). Is this possible with Swift? If yes, how would I do it?

To explain the scenario further, I have a function which has a completion block that returns the response or error from a service call. In the block, the success object is in fact an Array of AnyObject where the dynamicType of the object is that of the calling class. 

    someObject.callService(classObject, withCompletionBlock: {(objectOrNil : [AnyObject]!, errorOrNil:NSError?) -> Void in
                if(errorOrNil != nil) {                        self.delegate.didFailWithError(errorOrNil)
                }
                else {
                   // Here objectOrNil is during runTime an Array of class X 
                   // X.response gives the response JSON
                   // In a particular scenario, I need to intercept the response before the delegate
                    self.delegate.didReceiveResponse(objectOrNil)
                }

                }, withProgressBlock: nil)

In the block objectOrNil is an array of a class X ([X]) where the X would be class invoking the service call. All the classes that call the method has a response dictionary object which is populated with the response after the service call is completed and the delegate invoked.

To handle a particular scenario, I need to intercept the service response (X.response) where X is objectOrNil[0] from within this block and do additional processing.

I'm able to see the class name when I do a 

po objectOrNil[0].dynamicType

in the console, but am unable to cast the objectOrNil[0] to the right type X to fetch X.response. When I tried 

po objectOrNil[0].response

I'm getting an error that response is ambiguous with NSURLResponse response. But 

po objectOrNil[0].response as NSDictionary

returns the right JSON response in console during runtime (with breakpoint).

However the below code gives a compile time error that AnyObject does not have response attribute.

let responseDict = objectOrNil[0].response as NSDictionary

Can anyone guide me on how to cast to the dynamicType type and fetch the response dictionary for me to proceed?

Thanks

Upvotes: 1

Views: 368

Answers (1)

vadian
vadian

Reputation: 285072

You could use a protocol

protocol Respondable {
  var response : NSDictionary {get}
}

and then constrain the type of objectOrNil to that protocol

someObject.callService(classObject, withCompletionBlock: {(objectOrNil : [Respondable]!, errorOrNil:NSError?) -> Void

Upvotes: 2

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