下面我們來看一篇關於Swift結構體指針操作的教程,希望這篇文章能夠幫助到各位朋友,希望文章能夠幫助到各位朋友的哦.

在c語言中申明一個變量並通過指針修改該變量的值

int a = 1;

int *p = &a;
*p = 2;

printf("a value is %d\\\\n",a);
a value is 2

c語言操作結構體指針操作

申明一個叫User的結構體

typedef struct User{
    int ID;
    int age;
} User;
申明一個結構體User變量user 設置ID值為1 age值為18

User user;
user.ID = 1;
user.age = 3;
通過指針對變量user的值進行修改

//申明一個結構體指針變量userpointer指向user的地址
User *userpointer = &user;

//修改ID的值為2
int  *idPointer = (int *)userpointer;
*idPointer = 2;

//獲得屬性age所在指針
int *agePointer = ++ idPointer;
//修改user的age值為4
*agePointer = 4;
printf("user ID = %d, age = %d", user.ID, user.age);
user ID = 2, age = 4

Swift

Swift並不推薦對指針進行直接操作,  但仍提供了幾種可以直接操作內存的指針類型，以下是c與Swift的語法對應表 ，使用 Type 做類型占用

對於返回值、變量和參數，使用一下對應表

C 語法 Swift 語法
const Type * UnsafePointer
Type * UnsafeMutablePointer
對於類，使用一下語法對應

C 語法 Swift 語法
Type const UnsafePointer
Type __strong UnsafeMutablePointer
Type ** AutoreleasingUnsafeMutablePointer
在Swift中無類型的指針，原始內存可以用UnsafeRawPointer 和UnsafeMutableRawPointer來表示

如果像不完整結構體的這樣的c指針的值的類型無法用Swift來表示，則用OpaquePointer來表示

更多指針相關知識詳見 文檔

接下來，進行Swift版結構體指針操作

申明User結構體

struct User {
    var ID: Int
    var age: Int
}
申明變量，並獲取變量地址, 創建一個user變量 ID初始值問為1 age初始值為3

通過指針設置ID值為2 設置age值為3

var user = User(ID: 1, age: 3)
let userPointer = withUnsafePointer(to: &user, {$0})//UnsafePointer

 
//打印user指針的值
print(userPointer.pointee)
//User(ID: 1, age: 3)

//獲取user ID的指針
let userIDPointer = unsafeBitCast(userPointer, to: UnsafeMutablePointer
 
  .self)
//設置ID的值為2
userIDPointer.pointee = 2
print(userPointer.pointee)
//User(ID: 2, age: 3)

//獲取user age的指針
let agePointer = userIDPointer.advanced(by: 1)
agePointer.pointee = 4
print(userPointer.pointee)
//User(ID: 2, age: 4)
 
雖然c和Swift的語法差距有點大，但是原理是相同的

接下來我們看一個更復雜一點的例子

public struct Person {
      var age: Int
      var firstName: String
      var lastName: String
      var phoneNumber: PhoneNumber
}
public struct PhoneNumber {
      var number: String
      var type: String
}
創建person變量 並通過指針操作 獲取對應的屬性值

let phone = PhoneNumber(number: "186xxxxxxxx", type: "work")
var person = Person(age: 24, firstName: "Bing", lastName: "lin", phoneNumber: phone)
let rawPointer = withUnsafePointer(to: &person, { UnsafeRawPointer($0)})

let age = rawPointer.load(fromByteOffset: 0, as: Int.self)
let firstName = rawPointer.load(fromByteOffset: 8, as: String.self)
let lastName  = rawPointer.load(fromByteOffset: 32, as: String.self)
let phoneInfo = rawPointer.load(fromByteOffset: 56, as: PhoneNumber.self)

print("age: \\\\(age) firstName: \\\\(firstName) lastName: \\\\(lastName) , phoneNumber: \\\\(phoneInfo)")
//age: 24 firstName: Bing lastName: lin , phoneNumber: PhoneNumber(number: "186xxxxxxxx", type: "work")
到這裡，我們已經學會了 通過指針獲取值，通過指針設置對應的值

接下來 就可以運用這些知識發揮自己的創造力了