如何将Objective-C块转换为Swift闭包？

Question

I have the following Objective-C block assignment example from Github dzenbot/DZNPhotoPickerController that I am struggling to convert to Swift. Controller is a UIImagePickerController.

controller.finalizationBlock = ^(UIImagePickerController *picker, NSDictionary *info) {

    UIImage *image = info[UIImagePickerControllerEditedImage];
    weakSelf.imageView.image = image;

    // Dismiss when the crop mode was disabled
    if (picker.cropMode == DZNPhotoEditorViewControllerCropModeNone) {
        [weakSelf dismissController:picker];
    }
};

I have tried the following, but cannot figure out where I am going wrong.

controller.finalizationBlock = { (picker: UIImagePickerController, info: NSDictionary) -> UIImagePickerControllerFinalizationBlock! in
        var image = UIImagePickerControllerEditedImage(info)
        imageView.image = image

        // Dismiss when the crop mode was disabled
        if (picker.cropMode == .None) {
            dismissEditor(picker)
        }
    }

The error I get is:

"Cannot assign value of type '(UIImagePickerController, NSDictionary) -> UIImagePickerControllerFinalizationBlock!' to type 'UIImagePickerControllerFinalizationBlock!'

Answer 1

The Objective-C block does not return anything, so the closure for the same should look like this:

controller.finalizationBlock = { (picker, info) in
        var image = UIImagePickerControllerEditedImage(info)
        imageView.image = image

        // Dismiss when the crop mode was disabled
        if (picker.cropMode == .None) {
            dismissEditor(picker)
        }
    }

Answer 2

The Objective-C block returns nothing,

controller.finalizationBlock = { (picker: UIImagePickerController, info: NSDictionary) -> (Void) in
        var image = UIImagePickerControllerEditedImage(info)
        imageView.image = image

        // Dismiss when the crop mode was disabled
        if (picker.cropMode == .None) {
            dismissEditor(picker)
        }
    }

Note 1. If you're going to use the closure in other functions you can declare an Alias in order to provides more readable code (But It's not mandatory)

typealias UIImagePickerControllerFinalizationBlock = (picker: UIImagePickerController, info: NSDictionary) -> (Void)

Note 2. Maybe you can make the info parameter type more " Swifty " with [String: AnyObject] or whatever the type info parameter uses.

Answer 3

Try this it may help you :

controller.finalizationBlock = {(picker: UIImagePickerController, info: [NSObject : AnyObject]) -> Void in
     var image: UIImage = info[UIImagePickerControllerEditedImage]
     weakSelf.imageView.image = image
    // Dismiss when the crop mode was disabled
     if picker.cropMode == DZNPhotoEditorViewControllerCropMode.None 
     {
         weakSelf.dismissController(picker)
     }
}