Question: What is the the imageWasSavedSuccessfully function?

Transcript – Question: What is the the imageWasSavedSuccessfully function?

In this video, we’ll take a quick look at the Swift method imageWasSavedSuccessfully when taking pictures with our iOS camera.

Hi, I’ve been getting many questions in the comments, so I figure it’s time we start answering some in their own videos.

Question: What is the the imageWasSavedSuccessfully function?

In the “How to access the iOS camera using Swift 2.0”, 00bikeboy asks “The transcript doesn’t go into the imageWasSavedSuccessfully function. Any chance you could go over this part of the code?” Absolutely! Let’s take a deeper look at the method.

If you remember from the Swift iOS camera tutorial, these were the basic steps to taking a photo. We get access, check to see if we can use the camera, present a camera view controller, check to see if we have an image, and then do something with it. The area we’re focusing on for this question is what we do with the image.

Steps to access camera

What we did in the video was save the image to the photos album. iOS calls didFinishPickingMediaWithInfo once we have selected a photo, either by selection or taking a photo. We then called UIImageWriteToSavedPhotosAlbum. This saves the photo to the photo album, and from there we can provide another function to call once the image is written.

func imagePickerController(picker: UIImagePickerController, 
                    didFinishPickingMediaWithInfo info: [String : AnyObject]) {

    print("Got an image")

    if let pickedImage:UIImage = (info[UIImagePickerControllerOriginalImage]) as? UIImage {

        let selectorToCall = Selector("imageWasSavedSuccessfully:didFinishSavingWithError:context:")
        UIImageWriteToSavedPhotosAlbum(pickedImage, self, selectorToCall, nil)
    }

    imagePicker.dismissViewControllerAnimated(true, completion: {
        // Anything you want to happen when the user saves an image
    })

}

The selector is imageWasSavedSuccessfully. This is a user defined function, and we can put anything we want into it.

func imageWasSavedSuccessfully(image: UIImage, didFinishSavingWithError error: NSError!, 
                               context: UnsafeMutablePointer<()>){

    print("Image saved")
    if let theError = error {
        print("An error happened while saving the image = \(theError)")
    } else {
        print("Displaying")
        dispatch_async(dispatch_get_main_queue(), { () -> Void in
             self.currentImage.image = image
        }       
    }
}

What we put in the function was a check to make sure it was successfully saved. If it didn’t we’d get an error object. If not, the image was saved so I’m updating the UI to display the image on a background thread.

So that’s what we were doing in the imageWasSavedSuccessfully selector. To recap, it’s a user defined selector we passed to UIImageWriteToSavedPhotosAlbum. The method can do anything we want, but in our case we just updated the UI with the new image.

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See you in the next video!