Can not use Objective-c block in swift

Question

I have decelerated this blocks in my objective-c code:

typedef void(^ActionStringDoneBlock)(ActionSheetStringPicker *picker, NSInteger selectedIndex, id selectedValue);
typedef void(^ActionStringCancelBlock)(ActionSheetStringPicker *picker);

I decelerate an instance of this blocks in objective-c like below:

ActionStringDoneBlock done = ^(ActionSheetStringPicker *picker, NSInteger selectedIndex, id selectedValue) {
    selectedVisa = (int) selectedIndex;
    if ([visaView.textField respondsToSelector:@selector(setText:)]) {
        [visaView.textField performSelector:@selector(setText:) withObject:selectedValue];
    }
};

and use this instance like below:

    [ActionSheetStringPicker showPickerWithTitle:"myTitle"
                                        rows:visaData
                            initialSelection:initialSelection
                                   doneBlock:done
                                 cancelBlock:cancel
                                      origin:visaView.textField
 ];

My project users both swift and objective-c code. Now I want to use these code in a new ViewController in my swift code. I use below code:

let done = {(picker: ActionSheetStringPicker?, selectedIndex:Int, selectedValue: Any?)  in

    //My Codes

    }

    let cancel  = {
        (_ picker: ActionSheetStringPicker) -> Void in

    }

    ActionSheetStringPicker.show(withTitle: "My Title",
                                 rows: messageTitleData,
                                 initialSelection: initialSelection,
                                 doneBlock: done as ActionStringDoneBlock,
                                 cancel: cancel as! ActionStringCancelBlock,
                                 origin: messageTitle.textField
    )

but I get below error in swift code:

EXC_BREAKPOINT

I had printed the out put of done as ActionStringDoneBlock to the console an I see below result:

error: :3:1: error: cannot convert value of type '() -> ()' to type 'ActionStringDoneBlock' (aka '(Optional, Int, Optional) -> ()') in coercion

I also tried defining done as below:

  let done = {(picker: Optional<ActionSheetStringPicker>, selectedIndex:Int, selectedValue: Optional<Any>)  in

    //My Codes

    }

but again got same error. Does someone have any idea about whats the problem in the swift code?

score 5 · Accepted Answer · answered Jul 11 '17 at 09:40

You need to annotate the closure types and omit the passed types

let done : ActionStringDoneBlock  = { (picker, selectedIndex, selectedValue)  in ... }

let cancel : ActionStringCancelBlock = { picker in ... }

Without an annotation a closure is treated as () -> (). That's what the error message says.

Can not use Objective-c block in swift

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