猫鼬-'pre'中间件返回错误 [英] Mongoose - Return error in 'pre' middleware

问题描述

如果在schema.pre('save')中验证失败，如何发送自定义错误消息?例如，如果我具有聊天功能，可以在其中创建新对话，那么我想检查与给定参与者的对话是否已经存在，因此我可以这样做:

How can I send a custom error message if my validation fails in schema.pre('save')? For example, if I have a chat feature, where you create a new conversation, I want to check if a conversation with the given participants already exists, so I can do:

ConversationSchema.pre('save', function(next, done) {
    var that = this;
    this.constructor.findOne({participants: this.participants}).then(function(conversation) {
        if (conversation) {
            // Send error back with the conversation object
        } else {
            next();
        }
    });
});

推荐答案

在调用next报告错误时传递Error对象:

Pass an Error object when calling next to report the error:

ConversationSchema.pre('save', function(next, done) {
    var that = this;
    this.constructor.findOne({participants: this.participants}).then(function(conversation) {
        if (conversation) {
            var err = new Error('Conversation exists');
            // Add conversation as a custom property
            err.conversation = conversation;
            next(err);
        } else {
            next();
        }
    });
});

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