类和结构都可以做到:

定义属性来存储值 定义提供功能的方法 被扩展 遵守协议 定义初始化 定义下标以提供对其变量的访问

唯一的类可以做到:

继承 铸字 定义deinitialisers 允许多个引用进行引用计数。

下面是一个类的例子。请注意，当名称更改时，两个变量引用的实例将如何更新。鲍勃现在是苏了，所有提到鲍勃的地方都是这样。

class SomeClass {
    var name: String
    init(name: String) {
        self.name = name
    }
}

var aClass = SomeClass(name: "Bob")
var bClass = aClass // aClass and bClass now reference the same instance!
bClass.name = "Sue"

println(aClass.name) // "Sue"
println(bClass.name) // "Sue"

现在使用结构体，我们看到值被复制，每个变量保留自己的值集。当我们将名称设置为Sue时，aStruct中的Bob结构体不会被更改。

struct SomeStruct {
    var name: String
    init(name: String) {
        self.name = name
    }
}

var aStruct = SomeStruct(name: "Bob")
var bStruct = aStruct // aStruct and bStruct are two structs with the same value!
bStruct.name = "Sue"

println(aStruct.name) // "Bob"
println(bStruct.name) // "Sue"

所以对于表示有状态的复杂实体来说，类是非常棒的。但是对于仅仅是测量值或相关数据位的值，结构体更有意义，这样您可以轻松地复制它们并使用它们计算或修改值，而不用担心副作用。

以上答案都是正确的，我希望我的回答能帮助到那些不理解以上答案的人。

在Swift中有两种类型的对象

结构体 类

它们之间的主要区别是

Struct是值类型 类是引用类型

例如这里的代码要理解得很好。

struct SomeStruct {
var a : Int;

init(_ a : Int) {
    self.a = a
}
}

class SomeClass {
var a: Int;

init(_ a: Int) {
    self.a = a
}

}
var x = 11

var someStruct1 = SomeStruct(x)
var someClass1 = SomeClass(x)

var someStruct2 = someStruct1
var someClass2 = someClass1

someClass1.a = 12
someClass2.a // answer is 12 because it is referencing to class 1     property a

someStruct1.a = 14
someStruct2.a // answer is 11 because it is just copying it not referencing it

这是主要的区别，但我们也有次要的区别。

类

必须声明初始化式(构造函数) 有deinitialisers 可以从其他类继承吗

结构体

它为你提供了自由初始化器，你不必声明初始化器，如果你声明了自由初始化器，它将被你声明的初始化器覆盖 没有去初始化 不能从其他结构继承

Usually (in most programming languages), objects are blocks of data that are stored on heap, and then a reference (normally a pointer) to these blocks, contains a name is using to access these blocks of data. This mechanism allows sharing objects in the heap by copying the value of their references (pointers). This is not the case of basic data types such as Integers, and that is because the memory needed to create a reference is almost the same as the object (in this case integer value). Thus, they will be passed as values not as a reference in the case of large objects.

Swift使用struct来提高String和Array对象的性能。

这是一本很好的读物

这个问题似乎是重复的，但无论如何，下面的问题将回答大多数用例:

One of the most important differences between structures and classes is that structures are value types and are always copied when they are passed around in your code, and classes are reference type and are passed by reference. Also, classes have Inheritance which allows one class to inherit the characteristics of another. Struct properties are stored on Stack and Class instances are stored on Heap hence, sometimes the stack is drastically faster than a class. Struct gets a default initializer automatically whereas in Class, we have to initialize. Struct is thread safe or singleton at any point of time.

而且, 要总结结构和类之间的区别，有必要了解值类型和引用类型之间的区别。

在复制值类型时，它将从其中复制所有数据 你要复制到新变量中的东西。它们是分开的 事物和改变一个并不影响另一个。 复制引用类型时，新变量引用 与你要复制的东西相同的内存位置。这意味着 改变一个会改变另一个因为它们都指向 相同的内存位置。 下面的示例代码可以作为参考。

/ / sampleplayground.playground

  class MyClass {
        var myName: String
        init(myName: String){
            self.myName = myName;
        }
    }

    var myClassExistingName = MyClass(myName: "DILIP")
    var myClassNewName = myClassExistingName
    myClassNewName.myName = "John"


    print("Current Name: ",myClassExistingName.myName)
    print("Modified Name", myClassNewName.myName)

    print("*************************")

    struct myStruct {
        var programmeType: String
        init(programmeType: String){
            self.programmeType = programmeType
        }
    }

    var myStructExistingValue = myStruct(programmeType: "Animation")
    var myStructNewValue = myStructExistingValue
    myStructNewValue.programmeType = "Thriller"

    print("myStructExistingValue: ", myStructExistingValue.programmeType)
    print("myStructNewValue: ", myStructNewValue.programmeType)

输出:

Current Name:  John
Modified Name John
*************************
myStructExistingValue:  Animation
myStructNewValue:  Thriller

Struct是值类型。这意味着，如果你将结构的实例复制到另一个变量，它只是复制到变量。

值类型示例

struct Resolution {
    var width = 2
    var height = 3
}

let hd = Resolution(width: 1920, height: 1080)
var cinema = hd //assigning struct instance  to variable
println("Width of cinema instance is \(cinema.width)")//result is 1920
println("Width of hd instance is \(hd.width)")//result is 1920

cinema.width = 2048

println("Width of cinema instance is \(cinema.width)")//result is 2048
println("Width of hd instance is \(hd.width)")//result is 1920

类是引用类型。这意味着如果将类的一个实例赋值给一个变量，它将只保存对该实例的引用，而不是副本。