为什么`Tags.findOne()；‘返回一个TypeError？

Question

如果标签不存在，/tag [tag name]命令应该发送标记描述或消息。目前我没有在模型中的项目。当我使用任何参数运行该命令时，就会得到TypeError: Cannot read properties of undefined (reading 'findOne')。这是我的代码：

commands/tag.js

const { Tags } = require('../models/tag.js');
const { SlashCommandBuilder } = require('discord.js');

module.exports = {
    data: new SlashCommandBuilder()
        .setName('tag')
        .setDescription('Show a tag.')
        .addStringOption(option =>
            option
                .setName('name')
                .setDescription('The name of the tag')
                .setRequired(true)
        ),
    async execute(interaction) {
        const name = interaction.options.getString('name');

        const tag = Tags.findOne({where: { name: name } });

        if (tag) return interaction.reply(tag.get('description'));

        return interaction.reply('That tag doesn\'t exist!');
    }
}

模型/tag.js

module.exports = (db, DataTypes) => {
    return db.define('tags', {
        name: {
            type: DataTypes.STRING,
            unique: true,
        },
        description: DataTypes.TEXT,
    });
}

db-init.js (这是手动运行的)：

const { Sequelize, DataTypes } = require('sequelize');

const db = new Sequelize({
    dialect: 'sqlite',
    storage: './database.sqlite',
});

require('./models/tag.js')(db, DataTypes);

const force = process.argv.includes('--force') || process.argv.includes('-f');

db.sync({ force }).then(async () => {
    console.log('Database synced.');

    db.close();
}).catch(console.error);

commands/addTag.js

const { Tags } = require('../models/tag.js');
const { SlashCommandBuilder } = require('discord.js');

module.exports = {
    data: new SlashCommandBuilder()
        .setName('addtag')
        .setDescription('Create a tag!')
        .addStringOption(option =>
            option
                .setName('name')
                .setDescription('The name of your tag')
                .setRequired(true)    
        )
        .addStringOption(option =>
            option
                .setName('description')
                .setDescription('The tag description')
                .setRequired(true)
        ),
    async execute(interaction) {
        const name = interaction.options.getString('name');
        const description = interaction.options.getString('description');

        try {
            const tag = await Tags.create({
                name: name,
                description: description,
            });

            return interaction.reply(`Tag \`${tag.name}\` created.`);
        } catch (error) {
            if (error.name = 'SequelizeUniqueConstraintError') return interaction.reply('That tag already exists!');

            return interaction.reply({ content: 'An error occured.', ephemeral: true });
        }
    }
}

如果标签已经存在，/addtag [tag name] [tag description]命令应该创建标记或发送消息。每当我运行这个命令时，我都不会收到任何错误，但是bot说标签已经存在了，尽管它并不存在。请有人解释一下为什么这些命令不能正常工作吗？

Answer 1

我可以看到，您正在使用Sequelize与SQLite数据库进行交互。为了使用findOne方法，需要使用在db-init.js中创建的db对象来访问Tags模型，然后调用该对象上的findOne方法。

下面是如何修复您的tag.js文件：

const { db } = require('../db-init.js');
const { Tags } = require('../models/tag.js')(db, DataTypes); // This line is changed
const { SlashCommandBuilder } = require('discord.js');

module.exports = {
    data: new SlashCommandBuilder()
        .setName('tag')
        .setDescription('Show a tag.')
        .addStringOption(option =>
            option
                .setName('name')
                .setDescription('The name of the tag')
                .setRequired(true)
        ),
    async execute(interaction) {
        const name = interaction.options.getString('name');

        // This is the new code
        const tag = await Tags.findOne({ where: { name: name } }); // Notice the use of await here
        if (!tag) return interaction.reply('That tag doesn\'t exist!');
        return interaction.reply(tag.get('description'));
    }
}

addTag.js文件中的问题是在比较中使用SequelizeUniqueConstraintError错误名称而不是赋值。在JavaScript中，赋值运算符=不同于比较运算符==。赋值运算符为变量分配值，而比较运算符检查两个值是否相等。

下面是如何修复您的addTag.js文件：

const { db } = require('../db-init.js');
const { Tags } = require('../models/tag.js')(db, DataTypes); // This line is changed
const { SlashCommandBuilder } = require('discord.js');

module.exports = {
    data: new SlashCommandBuilder()
        .setName('addtag')
        .setDescription('Create a tag!')
        .addStringOption(option =>
            option
                .setName('name')
                .setDescription('The name of your tag')
                .setRequired(true)    
        )
        .addStringOption(option =>
            option
                .setName('description')
                .setDescription('The tag description')
                .setRequired(true)
        ),
    async execute(interaction) {
        const name = interaction.options.getString('name');
        const description = interaction.options.getString('description');

        try {
            const tag = await Tags.create({
                name: name,
                description: description,
            });

            return interaction.reply(`Tag \`${tag.name}\` created.`);
        } catch (error) {
            // This is the new code
            if (error.name === 'SequelizeUniqueConstraintError') return interaction.reply('That tag already exists!');

            return interaction.reply({ content: 'An error occured.', ephemeral: true });
        }
    }
}