If I declare an empty image:
var myImage: UIImage?
and then give it a value:
myImage = UIImage(named: "drawing.png")
how can I later remove that value, returning it to its original empty state?
var myImage: UIImage?
Is basically short hand for making a UIImage
point to nil
automatically.
So to reset it back to the original value say:
myImage = nil
将其值设置为nil,就像这样
myImage = nil
只需为它指定nil
:
myImage = nil
Optional
is an enum
type in Swift; it has two cases:
enum Optional<T> : NilLiteralConvertible {
case None
case Some(T)
...
}
By assigning an image to your Optional<UIImage>
, you have implicitly specified .Some(image)
. To clear it, you can use .None
. But since Optional
also conforms to NilLiteralConvertible
, you can use the simpler and clearer nil
.
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.