poster typeerror用户不是函数

我使用Nodejs和mongodb来练习开发网站，但遇到了一个问题。我的server.js代码如下：

var express=require('express');
var morgan=require('morgan');
var mongoose=require('mongoose');
var bodyParser=require('body-parser');
var User=require('./models/user');
var app=express();
mongoose.connect('mongodb://root:abc123@ds021172.mlab.com:21172/test', function(err){
  if(err){
    console.log(err);
  } else{
    console.log("Connected to the database");
  }
});
//Middleware
app.use(morgan('dev'));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: true}));
app.post('/create-user', function(req, res, next){
  var user=new User();
  user.profile.name=req.body.name;
  user.password=req.body.password;
  user.email=req.body.email;
  user.save(function(err){
    if(err) return next(err);
    res.json('Successfully created a new user');
  });
});

app.listen(3000, function(err){
  if(err) throw err;
  console.log("Server is running on port 3000");
});

我的user.js代码如下：

var mongoose=require('mongoose');
var bcrypt=require('bcrypt-nodejs');
var Schema=mongoose.Schema;
/* The user schema attribution / chatacteristics / field */
var UserSchema = new mongoose.Schema({
  email: {type: String, unique: true, lowercase: true},
  password: String,
  profile: {
    name: {type: String, default: ''},
    picture: {type: String, default: ''}
  },
  address: String,
  history: [{
    date: Date,
    paid: {type: Number, default: 0},
    //item{type: Schema.Types.ObjectId, ref: ''}
  }]
});
/* Hash the password before we even save it to the datebase  */
UserSchema.pre('save', function(next){
  var user=this;
  if(!user.isModified('password')) return next();
  bcrypt.genSalt(10, function(err, salt){
    if(err) return next(err);
    bcrypt.hash(user.password, salt, null, function(err, hash){
      if(err) return next(err);
      user.password=hash;
      next();
    });
  });
});
/* compare password in the database and the one that the user type in */
UserSchema.methods.comparePassword=function(password){
  return bycrypt.compareSync(password, this.password);
}
module.exports=mongoose.model('User', UserSchema);

但是当我使用poster尝试发布如下数据时：

在此处输入图像描述

我输入了三个参数，姓名、密码、电子邮件并点击帖子按钮，我得到了错误：

TypeError: User is not a function
<br> &nbsp; &nbsp;at /Users/chengyuanying/ecommerce/server.js:27:12
<br> &nbsp; &nbsp;at Layer.handle [as handle_request] (/Users/chengyuanying/ecommerce/node_modules/express/lib/router/layer.js:95:5)
<br> &nbsp; &nbsp;at next (/Users/chengyuanying/ecommerce/node_modules/express/lib/router/route.js:131:13)
<br> &nbsp; &nbsp;at Route.dispatch (/Users/chengyuanying/ecommerce/node_modules/express/lib/router/route.js:112:3)
<br> &nbsp; &nbsp;at Layer.handle [as handle_request] (/Users/chengyuanying/ecommerce/node_modules/express/lib/router/layer.js:95:5)
<br> &nbsp; &nbsp;at /Users/chengyuanying/ecommerce/node_modules/express/lib/router/index.js:277:22
<br> &nbsp; &nbsp;at Function.process_params (/Users/chengyuanying/ecommerce/node_modules/express/lib/router/index.js:330:12)
<br> &nbsp; &nbsp;at next (/Users/chengyuanying/ecommerce/node_modules/express/lib/router/index.js:271:10)
<br> &nbsp; &nbsp;at urlencodedParser (/Users/chengyuanying/ecommerce/node_modules/body-parser/lib/types/urlencoded.js:95:37)
<br> &nbsp; &nbsp;at Layer.handle [as handle_request] (/Users/chengyuanying/ecommerce/node_modules/express/lib/router/layer.js:95:5)
<br> &nbsp; &nbsp;at trim_prefix (/Users/chengyuanying/ecommerce/node_modules/express/lib/router/index.js:312:13)
<br> &nbsp; &nbsp;at /Users/chengyuanying/ecommerce/node_modules/express/lib/router/index.js:280:7
<br> &nbsp; &nbsp;at Function.process_params (/Users/chengyuanying/ecommerce/node_modules/express/lib/router/index.js:330:12)
<br> &nbsp; &nbsp;at next (/Users/chengyuanying/ecommerce/node_modules/express/lib/router/index.js:271:10)
<br> &nbsp; &nbsp;at jsonParser (/Users/chengyuanying/ecommerce/node_modules/body-parser/lib/types/json.js:107:37)
<br> &nbsp; &nbsp;at Layer.handle [as handle_request] (/Users/chengyuanying/ecommerce/node_modules/express/lib/router/layer.js:95:5)

你能帮我解决这个问题吗？