如何在motoko中遍历内部数组？

Question

我刚接触过Motoko和网络电脑，当我工作的时候，我遇到了太多的困难，看起来很简单，我在做这件事时遇到了困难，我在这里发布了论坛问题的链接。

https://forum.dfinity.org/t/how-to-traverse-inner-array-of-a-trie/12941?u=manubodhi

如果有人精通Motoko和Dfinity，请帮忙

Answer 1

我在motoko操场为您准备了一个小代码，以了解如何遍历内部数组并实现过滤Trie的目标。以下是motoko操场上保存的项目：https://m7sm4-2iaaa-aaaab-qabra-cai.raw.ic0.app/?tag=1150943578

快速筛选内部数组，您可以使用：

let trieOfDishes = Trie.filter<DishId, Dish>(dishes, func (k, v) {
    Array.find<MealTypeId>(v.mealTypeId, func(x : MealTypeId) { x == mealTypeId }) != null ;
});

全面实施毒气罐守则：

import Trie "mo:base/Trie";
import Array "mo:base/Array";
import Iter "mo:base/Iter";
import Nat32 "mo:base/Nat32";

actor Dishes {
    
    type DishId = Nat32;
    type DishTypeId = Nat32;
    type MealTypeId = Nat32;

    public type Dish = {
        dishId: DishId;
        dishTypeId : DishTypeId;
        mealTypeId : [MealTypeId]
    };

    var dishes: Trie.Trie<DishId, Dish> = Trie.empty();

    private func key(x : DishId) : Trie.Key<DishId> {
        return { hash = x; key = x };
    };
    
    public func add_dish(dish: Dish) : async Dish {
        dishes := Trie.replace(dishes, key(dish.dishId), Nat32.equal, ?dish).0;
        return dish;
    };

    public query func getDishesByDishId (dishTypeId : DishTypeId) : async [(DishId, Dish)] {
       let trieOfDishes = Trie.filter<DishId, Dish>(dishes, func (k, v) { v.dishId == dishTypeId } );
       let arrayOfDishes : [(DishId, Dish)] = Iter.toArray(Trie.iter(trieOfDishes));
       return arrayOfDishes;
    };

    public query func getDishesBymealTypeId (mealTypeId : MealTypeId) : async [(DishId, Dish)] {
       let trieOfDishes = Trie.filter<DishId, Dish>(dishes, func (k, v) {
            Array.find<MealTypeId>(v.mealTypeId, func(x : MealTypeId) { x == mealTypeId }) != null ;
       });
       let arrayOfDishes : [(DishId, Dish)] = Iter.toArray(Trie.iter(trieOfDishes));
       return arrayOfDishes;
    };
    
}