Rust Development -- the concept and application example of trait

Trait

One 、 Concept

1.Trait Concept
Trait It is the function of a certain type that can be shared with other types . It abstractly defines the sharing behavior between types ,Trait bounds It refers to that the generic type parameter is specified as a type that implements a specific behavior constraint .
2.Trait The role of

• Use as an interface .
• The type tag Copy,Sized, By type marking IDE Can recognize some fixed types of behavior .
• Generic qualification 、 Input and output parameters are used as generic restrictions .
• Abstract types are equivalent to dynamic language calls , Static call , Dynamic invocation 、 Dynamic distribution .
  3. Concepts and C++ The virtual function of is almost , The difference is rust There is no concept of class inheritance .

One 、Trait As an interface

1.Trait The definition of

// Use keywords trait Put the method signatures together , To define a set of behaviors necessary to achieve a certain purpose 
// Here we use the article as an example , All articles have titles and authors , Whether blog or thesis 
pub trait  Article
{
    
    // Only method signature , No specific implementation , There can be multiple ways 
    fn digest(&self) ->String;

    // Default implementation 
    fn aothor(&self)
    {
    
      println!(" Default implementation ");
    }
}

2. Realization Trait

pub struct WeChatArticle
{
    
    pub aothor : String,// author 
    pub title : String,// title 
    pub timestamp : String// Create timestamps 
}


pub struct Blog
{
    
    pub aothor : String,// author 
    pub title : String,// title 
    pub collect : u64// Number of collections 
}


// Implement for type trait
impl Article for Blog  
{
    
  fn digest(&self) ->String 
  {
    
    self.title.clone() + &self.title.clone() + &self.collect.to_string()
  } 
}

impl Article for WeChatArticle
{
    
  fn digest(&self) ->String 
  {
    
    self.title.clone() + &self.title.clone() + &self.timestamp.clone()
  } 
}

3. Use

use rust_demo::Blog;
use rust_demo::Article;
fn main() 
{
    
   let blog : Blog = Blog 
    {
     
        aothor:"matt".to_string(), 
        title:"Rust Trait  Application ".to_string(),
        collect: 20
     };
    println!("Blog aothor is {}",blog.digest());
}s

4.Trait Default implementation of

pub trait  article
{
    
    // This is Trait Default implementation of , If the type does not override this method , The default implementation is used 
    fn aothor(&self) ->String
    {
    
    	self.aothor.clone()
    }
    fn title(&self) ->String;
}

Two 、Trai Use as a parameter

1. Pass in as a parameter

//item Is to implement the Article This Trait The type of 
pub fn notify(item : impl Article)
{
    
  print!("Article digest {} \n",item.digest());
}

Use

fn main() 
{
    
   let blog : Blog = Blog 
    {
     
        aothor:"matt".to_string(), 
        title:" Blog posts ".to_string(),
        collect: 20
     };

    let wechar :WeChatArticle  = WeChatArticle
    {
     
        aothor:"matt".to_string(), 
        title:" WeChat official account ".to_string(),
        timestamp:"1324111889".to_string()
     };

     notify(blog);
     notify(wechar);
}

2. Generic formal writing

//item Is to implement the Article This Trait The type of , Generic writing is more friendly to incoming unused types 
pub fn notify<T:Article>(item_1: T,item_2 : T)
{
    
  print!("Article digest {} \n",item_1.digest());
}

3. Multiple Trait constraint

//item Is to implement the Article and Display Two Trait
pub fn notify<T:Article + Display>(item_1: T)
{
    
  print!("Article digest {} \n",item_1.digest());
}

Use where Clause realization Trait constraint

pub fn notify<T,U>(item_1: T,item_2 : U)
    where
        T : Article + Display, //T To show these two Trait constraint 
        U : Clone + Debug,
{
    
  print!("Article digest {} \n",item_1.digest());
}

3、 ... and 、 Realization Trait As return type

// Only the same type can be returned , An error will be reported if the code of an improper type is returned 
pub fn notify( b : bool) -> impl Article
{
    
    // This will give you an error 
    // if(true)
    // {
    
    // Blog 
    // { 
    // aothor:"matt".to_string(), 
    // title:" Blog posts ".to_string(),
    // collect: 20
    // }
    // }
    // else
    // {
    
    // WeChatArticle
    // { 
    // aothor:"matt".to_string(), 
    // title:" WeChat official account ".to_string(),
    // timestamp:"1324111889".to_string()
    // }
    // }
    WeChatArticle
    {
     
        aothor:"matt".to_string(), 
        title:" WeChat official account ".to_string(),
        timestamp:"1324111889".to_string()
    }
}