第四课 motoko源码

import List "mo:base/List";
import Iter "mo:base/Iter";
import Time "mo:base/Time";
import Principal "mo:base/Principal";
actor {
    public type Message = {
        content: Text;
        time: Time.Time;
    };
    public type Microblog = actor {
        follow: shared(Principal) -> async (); //添加关注对象
        follows: shared query () -> async ([Principal]);//返回关注列表
        post: shared (Text) -> async (); //发布新消息
        posts: shared query () -> async [Message]; //返回所有发布的新消息
        timeline: shared () -> async [Message]; //返回所有关注对象发布的消息
    };
    stable var followed : List.List<Principal> = List.nil();

    public shared func follow(id: Principal) :async () {
        followed := List.push(id, followed);
    };
    public shared  query func follows() : async [Principal] {
        List.toArray(followed)
    };

    stable var messages : List.List<Message> = List.nil();

    public shared(msg) func post(content: Text) : async (){
        //assert(Principal.toText(msg.caller) == "t5f3o-4jc2c-kedu6-zkclt-jygbq-llpj7-o5sjc-nlwal-l6mis-zk4mq-jae");
        let message : Message = {
            content = Principal.toText(msg.caller);
            time = Time.now();
        };
        messages := List.push(message, messages);
    };
    public shared query func posts(since: Time.Time): async [Message] {
        var all:List.List<Message> = List.nil();
        for(msg in Iter.fromList(messages)) {
            if(msg.time > since) {
                all := List.push(msg, all);
            }
        };
        List.toArray(all);
    };
    public shared func timeline(since: Time.Time) : async [Message] {
        var all:List.List<Message> = List.nil();
        for(id in Iter.fromList(followed)) {
            let canister : Microblog = actor(Principal.toText(id));
            let msgs = await canister.posts();
            for(msg in Iter.fromArray(msgs)) {
               if(msg.time > since) {
                    all := List.push(msg, all);
                }; 
            }
        };
        List.toArray(all);
    };
};