Calling Swift Closure Inside Closure

Question

I have the following code:

  twitterAPI?.verifyCredentialsWithUserSuccessBlock({ (userName, password) -> Void in


            twitterAPI?.getUserTimelin         


        

Answer 1

This is a really misleading error message. The problem is that the inner variable can't be of optional type so you need to if/let it.

Check this out in a playground...

class Foo:NSObject {
    func doThing(bug:Int,completion:((Void)->(Void))) {

    }
}

let woot = Foo()
var bar:Foo? = Foo()

bar?.doThing(7, completion: {});

woot.doThing(3, completion: {

     bar?.doThing(4, completion:{});

});

It doesnt compile and the message

Cannot convert the expression type '(IntegerLiteralConvertible, completion:()->()-$T3)' to type '()'

Isn't exactly illuminating to the problem.

So you unwrap the optional

woot.doThing(3, completion: {

    if let bar = bar {
        bar.doThing(4, completion:{});
    }

});

And it now compiles.

And to the other issue

If you check the STTwitterAPI.h header

- (NSObject *)getUserTimelineWithScreenName:(NSString *)screenName
                                                         successBlock:(void(^)(NSArray *statuses))successBlock
                                                           errorBlock:(void(^)(NSError *error))errorBlock;

is just a convenience for the full signature of this.

- (NSObject *)getUserTimelineWithScreenName:(NSString *)screenName
                                                              sinceID:(NSString *)sinceID
                                                                maxID:(NSString *)maxID
                                                                count:(NSUInteger)count
                                                         successBlock:(void(^)(NSArray *statuses))successBlock
                                                           errorBlock:(void(^)(NSError *error))errorBlock;

Obj-C to Swift bridging places everything after the the first selector chunk inside the brackets so convenience methods tend to confuse things by code completing but not providing the canonical case.

So in your case (without me having STTwitter) this is what you want.

twitterAPI?.verifyCredentialsWithUserSuccessBlock({ (userName, password) -> Void in

    if let twitterAPI = self.twitterAPI {
       twitterAPI.getUserTimelineWithScreenName("JohnSmith",sinceID:someID,maxID:anotherID,count:1000, successBlock: { (objects)[AnyObject]!) -> Void in

        }, errorBlock: { (error: NSError!) -> Void in

       })
   }


    }, errorBlock: { (error :NSError!) -> Void in


})

how you choose to populate sinceID , maxID and count is up to you . I've never used the API so won't guess. They might be nil'able