Rust development - Struct usage example

结构体

1.定义

pub struct User
{
    
    user_id : u32,
    user_name: String,
    is_vip : bool,
}

2.实例化
Here initialization must all assign values ​​to all members,不像C++,A value can be initialized individually

let user : User = User {
     user_id: 100, user_name: "matt".to_string(), is_vip: false};

simplify assignment,The field names in the structure can be omitted when the fields in the structure are the same as the declared assignment fields,The literal values ​​that follow are different,So the field name must be specified

	let user_id : u32 = 101;
    let user_name  = "matting".to_string();
    let vip = true;
    let user2:User = User {
     user_id, user_name, is_vip:vip};

3.获取值

let user_name = user.user_name;

4.可变访问,A struct must be declared mutable for variable access,All elements in a struct are mutable.

 let mut user : User = User {
     user_id: 100, user_name: "matt".to_string(), is_vip: false};
    
  user.user_name = "matt45m".to_string();

5.更新语法,When creating a new instance based on an instance,Update syntax can be used.…userThe values ​​representing the next two fields come from the first structure

 	let mut user : User = User {
     user_id: 100, user_name: "matt".to_string(), is_vip: false};
    let user_id : u32 = 101;
    
    let user2:User = User {
     user_id, ..user};

6.Tuple struct
Tuple struct The whole has a given name,But the elements inside have no names.

 struct Color(u8,u8,u8);
 let black = Color(0,0,0);

7.struct的方法（rust的struct类似于c++的类）

• 方法是在struct（enum、trait对象）的上下文中定义的.
• 方法的第一个参数是self,selfpoints to the called onestruct 实例（类似于C++的this指针）.
• 方法在 impl （implement）块中定义的 impl StructName {}
• The first parameter of the method can be used &self,It can also be acquired for ownership or variable borrowing,like other parameters.
• new方法可以构造struct,可以理解为构造函数

pub struct SlotNode
{
    
    user_name :String,
    start_node : u32,//开始节点
    end_node : u32,//结束节点
}

impl SlotNode 
{
    
    pub fn new() -> Self 
    {
    
       SlotNode {
     user_name: String::new(), start_node: 0, end_node: 1024}
    }

    pub fn get_end_node(&self) -> u32
    {
    
        self.end_node
    }
}

instantiation and access

let slot_node = SlotNode::new();
 println!("{}\n", slot_node.get_end_node());

8.struct继承
rust structInheritance does not existC++That powerful feature,And there is a big difference in concept,In fact, it is not inherited in the traditional sense.

// Define a struct similar to the parent class
#[derive(Debug)]
 struct Animal
{
    
    gender: String,
}
impl Animal 
{
    
     fn new(gender: String) -> Self 
     {
    
         Self {
     gender }
     }
 }
 impl Animal 
 {
    
     pub fn print_gender(&self) 
     {
    
         println!("Animal {}", self.gender);
     }

     fn set_gender(&mut self, gender: String) 
     {
    
         self.gender = gender;
     }
 }

// 定义子类
#[derive(Debug)]
struct Cat  
{
    
     animal: Animal,
     name: String,
 }
impl Cat  
{
    
     fn new(animal: Animal, name: &str) -> Self 
     {
    
        Self {
     animal , name: name.to_string()}
     }
 }
 impl Cat 
 {
    
     fn as_animal(&self) -> &Animal 
     {
    
         &self.animal
     }

     fn as_mut_animal(&mut self) -> &mut Animal 
     {
    
         &mut self.animal
     }
 }
 
 fn main() {
    
    let student = Animal::new("male".to_string());
    let mut tome = Cat ::new(student, "小橘");

    tome.animal.print_gender();
    tome.animal.set_gender("femininity".to_string());
    tome.animal.print_gender();

    println!("{:#?}", tome);

    let a: &Animal = tome.as_animal();
    a.print_gender();
    let a: &mut Animal = tome.as_mut_animal();
    a.set_gender("femininity".to_string());
    a.print_gender();
}