UIImages：我应该使用存储属性还是计算属性？

Question

I haven't thought about it much until today. Basically I'm in a situation in which I have the same UIImage appear multiple times in my ViewController s, and I'm not sure what the impact is.

class MyObjectA{
    private(set) var myName: String
    var myImage: UIImage? { UIImage(named: myName) }  //as computed property
}

class MyObjectB{
    private(set) var myName: String
    private(set) var myImage: UIImage?  //as stored property

    init(myName: String){
        self.myName = myName
        self.myImage = UIImage(named: myName)
    }
}

Consider a TableView, where each cell corresponds to an object. Is it bad having an image constantly being instantiated with myimageview.image = UIImage(named: myobject.imagename) versus just intantiating once and referencing it with myimageview.image = myobect.image ? Or does Swift do some super magic where it optimizes it under the hood, knowing that image was already loaded once?

Answer 1

iOS has an UIImage cache, so calling UIImage(named: myobject.imagename) multiple times for the same image is perfectly fine.

The documentation says

Use the init(named:in:compatibleWith:) method (or the init(named:) method) to create an image from an image asset or image file located in your app's main bundle (or some other known bundle). Because these methods cache the image data automatically , they're especially recommended for images that you use frequently.

Answer 2

The idea behind using a computed property or a stored one is when the value of the property being changed or not with time,so given ex.1

class MyObjectA{
    private(set) var myName: String
    var myImage: UIImage? { UIImage(named: myName) }  //as computed property

So if myName changes with time then you need to make myImage a computed property to always get the latest updated image, but if myName is being set only once then you need to make it a stored property