即使在成功之后，MongoDB实体也不会保存

This is the Model

这是模型

    var mongoose = require('mongoose'),
        Schema = mongoose.Schema;

    var PostSchema = new Schema({
        post_author: { type: Schema.ObjectId, ref: "User" },
        post_text: String,
        total_comments: { type: Number, 'default': 0 },
        total_likes: { type: Number, 'default': 0 },
        likes_users: [{ type: Schema.ObjectId, ref: "User" }],
        comments: [{ type: Schema.ObjectId, ref: "Comment" }],
        attachments: {
            images: [], videos: []
        },
        loc :  { type: {type:String}, coordinates: [Number]},
        isActive: { type: Boolean, 'default': true },
        createdAt: { type: Date, 'default': Date.now }
    });
    // PostSchema.index({loc: '2dsphere'});
    module.exports = mongoose.model('Post', PostSchema);

var CommentSchema = new Schema({
    comment_user: { type: Schema.ObjectId, ref: "User" },
    comment_text: String,
    isActive: { type: Boolean, 'default': true },
    createdAt: { type: Date, 'default': Date.now }
});

module.exports = mongoose.model('Comment', CommentSchema);
    var mongoose = r