附加图像后，可选的UIImage数组为nil

Question

I have created an optional UIImage array as the following

var images: [UIImage]?

Then I have a function that receives as parameter an UIImage array:

func process(_ images: [UIImage] {
    images.forEach {
        self.images?.append($0)
    }
    print("images nil?:", self.images == nil)
}

Somehow this function prints that my self.images is nil, even after appending objects to it; but if I change my forEach iteration to simply:

self.images = images

It now doesn't recognize that the global variable is nil.

Why does this happen?

Answer 1

您需要初始化一个数组。

var images: [UIImage]? = []

Answer 2

You have never initialised your images array. Before appending, please do this:

images = [UIImage]()

Answer 3

Initialize your array like this:

var images = [UIImage]()

Append the whole array at once like:

func process(_ images: [UIImage]) {
    self.images.append(contentsOf: images)
    print(self.images)
}

No need to make your array optional. Since if there is no images in the array it would be empty. Check for array count instead of making it optional.

Answer 4

Just you need to do this

var images = [UIImage]()
func process(_ images: [UIImage] {
    self.images = images
}