swift3新路程（9）结构体和类-优快云博客

本文通过示例对比了Swift中结构体与类在传递方式上的核心差异：结构体按值传递，而类按引用传递。展示了属性变化如何影响各自的实例。

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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.

上面这句话是官方文档的

我们可以看到结构的一些形式和类是基本相似的

但是他们有一个很大的区别就是，结构体是值引用，类的是址引用，可能这么说不太直观

我写了个例子，我们可以看一下

struct Hello {
    var firstName:String
    var secondName:String
    func sayHello() -> Void {
        print("Hello \(firstName) \(secondName)")
    }
}

var hello = Hello(firstName: "Liu", secondName: "Mingchuan")
var hello_1 = hello

hello.sayHello()
hello.secondName = "Ryoma"
hello.sayHello()

hello_1.sayHello()

class Hello2 {
    var firstName:String = ""
    var secondName:String = ""
    
    func sayHello() -> Void {
        print("Hello \(firstName) \(secondName)")
    }
}
var hello2 = Hello2()
var hello2_1=hello2

hello2.firstName = "Liu"
hello2.secondName = "Mingchuan"
hello2.sayHello()
hello2.secondName = "Ryoma"
hello2.sayHello()

输出

Hello Liu Mingchuan

Hello Liu Ryoma

Hello Liu Mingchuan

Hello Liu Ryoma

我们就可以看到结构体的hello改变属性之后，hello_1的属性并没有改变

而类的就不同了，当hello2的属性变调之后，hello2_1的属性也变了