Discord机器人婚姻系统报错：无法读取undefined的cache属性

我正在为Discord机器人开发婚姻系统，但无法判断目标用户是否已拥有“Married”角色。以下是我的代码：

const Discord = require('discord.js');
module.exports = {
    name: "marry",
    aliases: ['m'],
    description: "marry someone",


    async run(client, message, args) {

        const user = message.mentions.users.first() || client.users.get(args[0]);
        let marriedRole = message.guild.roles.cache.find(r => r.name === "Married");
        let singleRole = message.guild.roles.cache.find(r => r.name === "Single");

        let proposerID = message.author.id;
        let proposerName = message.author.username;
        if (user.roles.cache.some(marriedRole)) {
            let embed = new Discord.MessageEmbed()
            .setDescription(`Sorry **${user.tag}**, is already married!`);
            let messageEmbed = await message.channel.send({ embeds: [embed] });
        }
        if (message.member.roles.cache.some(role => role.name === 'Single')) {
            let embed = new Discord.MessageEmbed()
            .setDescription(`**${user.username}**, **${message.author.username}** is asking for your hand in marriage, would you like to accept?`);
            let messageEmbed = await message.channel.send({ embeds: [embed] });
            messageEmbed.react('✅');
            messageEmbed.react('❌');
        }
        if (message.member.roles.cache.some(role => role.name === 'Married')) {
            let embed = new Discord.MessageEmbed()
            .setDescription(`Sorry **${message.author.username}**, but you are already married!`);
            let messageEmbed = await message.channel.send({ embeds: [embed] });
        }

        }
}

运行时持续出现以下错误：

if (user.roles.cache.some(marriedRole)) {
^
TypeError: Cannot read properties of undefined (reading 'cache')

问题根源 #

1. user对象无roles属性：你获取的user是Discord全局用户对象（User类），仅包含用户的全局信息；而角色是服务器内的属性，只有服务器成员对象（GuildMember）才拥有roles属性。
2. 未处理user为空的情况：如果用户未提及任何人或输入ID无效，user会是undefined，访问user.roles直接触发报错。
3. roles.cache.some()用法错误：该方法需要传入回调函数，直接传入角色对象无法生效。

修复步骤 #

1. 获取服务器成员对象：替换全局用户获取方式，直接获取服务器成员（GuildMember），比如用message.mentions.members.first()或message.guild.members.fetch()。
2. 增加参数校验：先判断是否成功获取目标成员，若未获取到则提示用户。
3. 修正角色判断逻辑：用roles.cache.has(role.id)直接判断角色存在性，比some()更高效且避免重名问题。

修改后的完整代码 #

const Discord = require('discord.js');
module.exports = {
    name: "marry",
    aliases: ['m'],
    description: "marry someone",

    async run(client, message, args) {
        // 获取目标服务器成员：优先提及，再尝试ID查找
        const targetMember = message.mentions.members.first() || await message.guild.members.fetch(args[0]).catch(() => null);
        const marriedRole = message.guild.roles.cache.find(r => r.name === "Married");
        const singleRole = message.guild.roles.cache.find(r => r.name === "Single");

        // 校验目标成员是否有效
        if (!targetMember) {
            const embed = new Discord.MessageEmbed()
                .setDescription("请提及一个有效的服务器成员或输入正确的用户ID！");
            return message.channel.send({ embeds: [embed] });
        }

        // 检查目标是否已婚
        if (targetMember.roles.cache.has(marriedRole.id)) {
            const embed = new Discord.MessageEmbed()
                .setDescription(`抱歉，**${targetMember.user.tag}** 已经结婚了！`);
            return message.channel.send({ embeds: [embed] });
        }

        // 检查发起者是否已婚
        if (message.member.roles.cache.has(marriedRole.id)) {
            const embed = new Discord.MessageEmbed()
                .setDescription(`抱歉，**${message.author.username}**，你已经结婚了！`);
            return message.channel.send({ embeds: [embed] });
        }

        // 发起者为单身，发送求婚消息
        if (message.member.roles.cache.has(singleRole.id)) {
            const embed = new Discord.MessageEmbed()
                .setDescription(`**${targetMember.user.username}**，**${message.author.username}** 向你求婚了，你愿意接受吗？`);
            const messageEmbed = await message.channel.send({ embeds: [embed] });
            messageEmbed.react('✅');
            messageEmbed.react('❌');
        }
    }
}

额外说明 #

• 使用角色ID判断存在性，避免因角色重名导致的判断错误，同时查询效率更高。
• 每个条件分支后添加return，触发条件后终止后续代码执行，防止多个提示同时发送。
• 用catch(() => null)处理ID查找失败的情况，确保targetMember为空时能被正确校验。

内容的提问来源于stack exchange，提问作者John Hayes