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#[derive(Debug)]
//1.trait-bound
//2.指定多个trait trait-bound
//3.返回 trait的类型
fn print_information(item: impl GetInformation) {
  //这里只关心是否实现impl trait，然后调用item实现的方法即可
  println!("name = {}",item.get_name());
  println!("age = {}",item.get_age());
  }
//4. 使用trait bound语法糖将函数参数使用trait简化
fn print_information<T: GetInfromation>(item: T) {
  //这里只关心是否实现impl trait，然后调用item实现的方法即可
  println!("name = {}",item.get_name());
  println!("age = {}",item.get_age());
  }
trait GetName {
    fn get_name(&self) -> &String; 
  }
trait GetAge {
    fn get_age(&self) -> u32;
  }
//5.trait bound，多个trait使用
//5.1 第一种写法
fn print_information<T: GetName+Get>(item: T) { //对T实现这两个trait
    println!("name = {}",item.get_name());
    println!("age = {}",item.get_age());

  }
//5.2 第二种写法
//fn print_information<T>(item: T) 
//   where T: GetName+GetAge
//{ //对T实现这两个trait
//    println!("name = {}",item.get_name());
//    println!("age = {}",item.get_age());
//  }

pub struct Student {
    pub name: String,
    pub age: u32,
  }
pub struct Teacher {
    pub name: String,
    pub age: u32,
  }
impl GetName for Student {
    fn get_name(&self) -> &String {
        &self.name
      }
  }
impl GetName for Teacher {
    fn get_name(&self) -> &String {
        &self.name
      }
  }

impl GetAge for Student {
    fn get_age(&self) -> &String {
        &self.age
      }
  }
impl GetAge for Teacher {
    fn get_age(&self) -> &String {
        &self.age
      }
  }

//6. trait类型作为返回
fn produce_item_with_age() -> impl GetAge { //返回的东西实现了这个triat,返回必须是
//一个具体的类型,if和else中的不是同一个类型
//错误用法
//      let is = true;
//      if is {
//      Student {
//          name: String::from("xiaoming"),
//          age: 15,
//        }
//      }else {
//      Teacher {
//          name: String::from("xiaohu"),
//          age: 21,
//        }
//      }
      Student {
          name: String::from("xiaoming"),
          age: 15,

        }
  }
fn main() {
    let s = Student {name: "xiaoming".to_string(),age: 10};
    print_information(s);
    let s = produce_item_with_age();

  }
  • trait来简化largest函数
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fn largest<T: PartialOrd + Copy> (list: &[T]) -> T { //这里相当于泛型需要满足的条件

//第二种写法
//fn largest<T> (list: &[T]) -> T {
//  where T:PartialOrd+ Copy

//PartialOrd是需要进行数据比较的特征
    let mut larger = list[0];
    for &item in list.iter() {
        if item > larger {
            larger = item;
          }
      }
    larger
  }
fn main() {
    let number_list = vec![1,2,23,34,8,100];
    let max_number = largest(&number_list);
    println!("max_number = {}",max_number);

    let char_list = vec!['a','y','b'];
    let max_char = largest(&char_list);
    println!("max_char = {}",max_char);
  }