我无法在课堂上正确访问此属性

Posted 2023-03-14

【中文标题】我无法在课堂上正确访问此属性

【英文标题】：I can't access to this property correctly on my class

【发布时间】：2021-09-29 05:08:20

【问题描述】：

为什么我无法在我的运行函数中访问this.name 属性？

基本事件类：

import  ClientEvents  from 'discord.js';

import DiscordClient from './DiscordClient';

export default abstract class Event 
    readonly client: DiscordClient;
    readonly name: keyof ClientEvents | "raw";

    constructor(client: DiscordClient, name: keyof ClientEvents | "raw") 
        this.client = client;
        this.name = name;
    

    /**
     * Runs the event.
     * @param params Parameters
     */
    abstract run(...params: any | undefined): Promise<void>;

示例事件类：

import DiscordClient from '../structures/DiscordClient';
import Event from '../structures/Event';

export default class ReadyEvent extends Event 

    constructor(client: DiscordClient) 
        super(client, "ready");
        console.log(this.name); // Output: ready
    

    async run() 
        console.log(this.name); // Output: undefined
    

我正在注册这样的事件：(this.clientinstanceof DiscordClient)

/**
 * Registers single event.
 * @param event Event
 */
private registerEvent(event: any) 
    if (isConstructor(event, Event)) event = new event(this.client);
    else if (isConstructor(event.default, Event)) event = new event.default(this.client);
    if (!(event instanceof Event)) throw new Error(`Invalid event object to register: $event`);

    const evt = event as Event;

    if (this.events.some(e => e.name === evt.name)) throw new Error(`A event with the name "$evt.name" is already registered.`);

    this.events.set(evt.name, evt);
    this.client.on(evt.name as keyof ClientEvents, evt.run);

【问题讨论】：

你怎么打电话给run？如果您将run 函数作为回调传递到某处，则需要将其绑定到类，以便其this 指向正确的this，例如。 foo(readyEvent.run.bind(readyEvent)) 而不是 foo(readyEvent.run)

另见：How does the "this" keyword work?

我添加了我如何注册要提问的事件。你能再检查一遍吗？

【参考方案1】：

将evt.run 更改为evt.run.bind(evt)，以便使用正确的this 调用函数。

另见How does the "this" keyword work?"