swift - 快速复制对象数组

Question

我有一个名为 Meal 的类

class Meal {
    var name : String = ""
    var cnt : Int = 0
    var price : String = ""
    var img : String = ""
    var id : String = ""

    init(name:String , cnt : Int, price : String, img : String, id : String) {
        self.name = name
        self.cnt = cnt
        self.price = price
        self.img = img
        self.id = id
    }
}

我有一系列的餐食:

var ordered = [Meal]()

我想复制该数组，然后对其中一个中的 Meal 实例进行一些更改，而不更改第二个中的 Meal 实例，我该如何制作它的深拷贝？

此搜索结果对我没有帮助 How do I make a exact duplicate copy of an array?

Answer 1

因为 ordered 是一个 swift 数组，声明

 var orderedCopy = ordered

将有效地复制原始数组。

但是，由于 Meal 是一个类，新数组将包含引用与原始食物中提到的相同食物。

如果你也想复制膳食内容，这样改变一个数组中的膳食不会改变另一个数组中的膳食，那么你必须将膳食定义为一个结构，而不是一个类:

struct Meal { 
  ...

来自Apple book :

Use struct to create a structure. Structures support many of the same behaviors as classes, including methods and initializers. One of the most important differences between structures and classes is that structures are always copied when they are passed around in your code, but classes are passed by reference.