Objective-C Block in Swift - Variable Missing?

Question

Here's a block type that I am defining in objective-c

typedef void (^arrayBlock)(NSArray *blockArray);

I have an objective-c class with a method that uses this as a return block

-(void)loadTimesWithSuccessBlock:(arrayBlock)successBlock;

When I try to use this method in Swift, this is what autocomplete gives me.

let timeClockLibrarian = HMFTimeClockLibrarian()
timeClockLibrarian.loadTimesWithSuccessBlock { ([AnyObject]!) -> Void in
   //Where is blockArray?         
}

I'm assuming that [AnyObject]! is supposed to be the NSArray. But I don't see how I'm supposed to get access to that variable?

If I were to use this method in Objective-C I get a result like this:

[timeClockLibrarian loadTimesWithSuccessBlock:^(NSArray *blockArray) {
        //I can use the blockArray here :)
}];

zneak · Accepted Answer · 2015-09-04 14:50:31Z

1

[AnyObject]! is indeed only the type of the variable; autocomplete didn't name it. You just need to do something like (blockArray: [AnyObject]!).

let timeClockLibrarian = HMFTimeClockLibrarian()
timeClockLibrarian.loadTimesWithSuccessBlock { (blockArray: [AnyObject]!) -> Void in
   // your code here
}

answered Sep 4, 2015 at 14:50

zneak

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5 Comments

Hackmodford Over a year ago

That's what I thought. When I try to assign blockArray to a local variable i.e.{ var logEntries = [LogEntry() } using { self.logEntries = blockArray } it tells me "Cannot invoke 'loadTimesWithSuccessBlock' with an argument list of type '(([AnyObject]!) -> Void)'"

zneak Over a year ago

That's because the array is untyped and the assignment fails. You have different options depending on whether you use Xcode 6 or an Xcode 7 beta.

zneak Over a year ago

IIRC, that should be self.logEntries = blockArray as [LogEntry].

Hackmodford Over a year ago

Just tried it, and it wanted me to use as! instead of as. I'm not sure what that means, but it compiles now.

zneak Over a year ago

I wasn't sure which syntax was the correct syntax on Xcode 6, my bad. Glad it works. Also, at some point in the evolution of Xcode, it becomes possible to change the typedef on the Objective-C type to void (^arrayBlock)(NSArray<LogEntry>* __nonnull blockArray) or something along these lines, which lets Swift bridge the argument into a [LogEntry] without further complications.

Artyom Razinov · Accepted Answer · 2015-09-04 17:30:45Z

0

Write like this:

let timeClockLibrarian = HMFTimeClockLibrarian()
timeClockLibrarian.loadTimesWithSuccessBlock { blockArray in
   doSomething(blockArray)
}

If you want to refer to weak self use this:

let timeClockLibrarian = HMFTimeClockLibrarian()
timeClockLibrarian.loadTimesWithSuccessBlock { [weak self] blockArray in
   self?.doSomething(blockArray)
}

You may also want to get rid of implicit unwrapping. If so, specify nullability in Obj-C code:

typedef void (^arrayBlock)(nullable NSArray *blockArray);

answered Sep 4, 2015 at 17:30

Artyom Razinov

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