Swift Cast AnyObject to Block

问题

So I am using the Salesforce SDK and built bridging headers for the entire SDK.

They provide a block syntax which hasn't translated into the most usable code. For instance,

func sendRESTRequest(request: SFRestRequest!, failBlock: SFRestFailBlock!, completeBlock: AnyObject!)

The complete block is AnyObject!. I was able to get around this with

var block : @objc_block (dataResponse :AnyObject!) -> Void = { dataResponse in //I handle the response}
restService.sendRESTRequest(request, failBlock: { (error :NSError!) -> Void in

        }, completeBlock: unsafeBitCast(block, AnyObject.self))

So far this works fine. However, now I am trying to build unit testing for this code. I have created a mock class for SFRestAPI which is the class where the function "sendRESTRequest" resides. For testing purposes, I am trying to mock out the completeBlock: parameter by passing mock "data" that would be returned from the REST service.

class MockSFRestAPI : SFRestAPI {

    override func sendRESTRequest(request: SFRestRequest!, failBlock: SFRestFailBlock!, completeBlock: AnyObject!) {
        //Convert complete block into a closure and pass in some test data
    }
}

The issue is, I am unable to cast AnyObject! to a block like I was able to cast the block to AnyObject like above.

Some of my attempts have been:

var block = completeBlock as @objc_block (AnyObject! -> Void)
var block2: (AnyObject! -> Void) = unsafeBitCast(completeBlock, (@objc_block (AnyObject! -> Void)))

There have been many more attempts, but these are the only two that seem relatively sane. So, is this possible in Swift? The issue seems to be that I cannot provide a closure "type" to the second parameter of the unsafeBitCast method. I want to turn it into a closure so I can call it in my mock method and pass in some fake data.

回答1:

The best way to handle this situation is to create your own typealias for your block:

 typealias MyFunBlock = @objc_block (dataResponse :AnyObject!) -> Void;

Then you can use that to unsafebitcast:

var block: MyFunBlock = unsafeBitCast(completeBlock, MyFunBlock.self) as MyFunBlock;

来源：https://stackoverflow.com/questions/26738732/swift-cast-anyobject-to-block