ios - How to check if the image is saved [SWIFT]? -

how can check if image saved or not ? i'm saving way:

library.writeimagetosavedphotosalbum(image.cgimage, orientation: alassetorientation(rawvalue: image.imageorientation.rawvalue)!) { (url, error) -> void in 

after i'm calling alertcontroller , need make sure shows after user allowed save image.

the returning objects handled block, alassetslibrarywriteimagecompletionblock.

according apple's document:

alassetslibrarywriteimagecompletionblock = (nsurl!, nserror!) -> void 

where nserror object error described as:

if image not saved, error object describes reason failure, otherwise nil.

so in block, can like:

library.writeimagetosavedphotosalbum(image.cgimage, orientation: alassetorientation(rawvalue: image.imageorientation.rawvalue)!) {  (url, error) -> void in     if error != nil {         // handle error.     } else {         // saved successfully.     } }