建造者模式 rust和java的实现（二）

import java.util.ArrayList;
import java.util.List;
public class Meal {
   private List<Item> items = new ArrayList<Item>();    
   public void addItem(Item item){
      items.add(item);
   }
   public float getCost(){
      float cost = 0.0f;
      for (Item item : items) {
         cost += item.price();
      }        
      return cost;
   }
   public void showItems(){
      for (Item item : items) {
         System.out.print("Item : "+item.name());
         System.out.print(", Packing : "+item.packing().pack());
         System.out.println(", Price : "+item.price());
      }        
   }    
}

public class MealBuilder {
   public Meal prepareVegMeal (){
      Meal meal = new Meal();
      meal.addItem(new VegBurger());
      meal.addItem(new Coke());
      return meal;
   }   
   public Meal prepareNonVegMeal (){
      Meal meal = new Meal();
      meal.addItem(new ChickenBurger());
      meal.addItem(new Pepsi());
      return meal;
   }
}

public class BuilderPatternDemo {
   public static void main(String[] args) {
      MealBuilder mealBuilder = new MealBuilder();
      Meal vegMeal = mealBuilder.prepareVegMeal();
      System.out.println("Veg Meal");
      vegMeal.showItems();
      System.out.println("Total Cost: " +vegMeal.getCost());
      Meal nonVegMeal = mealBuilder.prepareNonVegMeal();
      System.out.println("\n\nNon-Veg Meal");
      nonVegMeal.showItems();
      System.out.println("Total Cost: " +nonVegMeal.getCost());
   }
}

Veg Meal
Item : Veg Burger, Packing : Wrapper, Price : 25.0
Item : Coke, Packing : Bottle, Price : 30.0
Total Cost: 55.0
Non-Veg Meal
Item : Chicken Burger, Packing : Wrapper, Price : 50.5
Item : Pepsi, Packing : Bottle, Price : 35.0
Total Cost: 85.5

// rsut trait不支持重名
pub trait Item {
    fn name(&self)->String;   
    fn price(&self)->f32;   
    fn packing(&self)->String;
}
// 汉堡实体类
struct ChickenBurger;
impl Item for ChickenBurger {
    fn name(&self)->String {
        String::from("ChickenBurger")
    }
    fn price(&self)->f32 {
        35.0
    }
    fn packing(&self)->String {
        String::from("Wrappper")
    }
}  
struct VegBurger;
impl Item for VegBurger {
    fn name(&self)->String {
        String::from("Pepsi")
    }
    fn price(&self)->f32 {
        35.0
    }
    fn packing(&self)->String {
        String::from("Wrappper")
    }
}  
// 饮料实体类
struct Pepsi;
impl Item for Pepsi {
    fn name(&self)->String {
        String::from("Pesi")
    }
    fn price(&self)->f32 {
        35.0
    }
    fn packing(&self)->String {
        String::from("Bottle")
    }
}  
struct Coke;
impl Item for Coke {
    fn name(&self)->String {
        String::from("Coke")
    }
    fn price(&self)->f32 {
        35.0
    }
    fn packing(&self)->String {
        String::from("Bottle")
    }
}  
struct Meal {
    items:Vec<Box<dyn Item>>,
}
impl Meal {
    fn add_item<T>(&mut self,item:Box<dyn Item>) 
    {
        self.items.push(item)
    }
    fn get_cost(&self)->f32{
        // 普通函数实现
        // let mut sum:f32=0.0; 
        // for i in self.items.iter()  {
        //     let price = i.price();
        //     sum+=price;
        // }
        // sum
        // 函数sji
        self.items.iter().fold(0.0, |acc, x| acc + x.price())
    }
    fn  show_items(&self){
        for  i in self.items.iter() {
            println!("{}",i.name());
            println!("{}",i.packing());
            println!("{}",i.price());
        }
    }
}
// 添加建造者
struct MealBuilder {}
impl  MealBuilder {
    fn prepareVegMeal()->Meal{
        let mut meal=Meal{items:Vec::new()};
        meal.add_item::<Box<dyn Item>>(Box::new(VegBurger{}));
        meal.add_item::<Box<dyn Item>>(Box::new(Coke{}));
        meal
    }
    fn prepareNonVegMeal()->Meal{
        let mut meal=Meal{items:Vec::new()};
        meal.add_item::<Box<dyn Item>>(Box::new(ChickenBurger{}));
        meal.add_item::<Box<dyn Item>>(Box::new(Pepsi{}));
        meal
    }
}
fn main() {
    let m=MealBuilder::prepareVegMeal();
    println!(" Veg Meal");
    m.show_items();
    println!("Total Cost : {}",m.get_cost());
    let m=MealBuilder::prepareNonVegMeal();
    println!(" \n\nNon-Veg Meal");
    m.show_items();
    println!("Total Cost : {}",m.get_cost());
}