node.js - Nodejs中间件.pre显示不是一个函数

Question

    var categoryList = new Referral({categoryList : category});

    categoryList.pre('save', function (next) {
        Referral.find({categoryList : category}, function (err, docs) {
            if (!docs.length){
                next();
            }else{
                console.log('Data exists: ', category);
                next(new Error("Data exists!"));
            }
        })
    })

Referral 是分配给我的架构的变量。categoryList 是对象

这会产生错误

TypeError: categoryList.pre is not a function at D:\Aventyn\ClipCare_v2\app\api.js:112:18 at Layer.handle [as handle_request] (D:\Aventyn\ClipCare_v2\node_modules\express\lib\router\layer.js:95:5) at next (D:\Aventyn\ClipCare_v2\node_modules\express\lib\router\route.js:131:13) at Route.dispatch (D:\Aventyn\ClipCare_v2\node_modules\express\lib\router\route.js:112:3) at Layer.handle [as handle_request] (D:\Aventyn\ClipCare_v2\node_modules\express\lib\router\layer.js:95:5) at D:\Aventyn\ClipCare_v2\node_modules\express\lib\router\index.js:277:22 at Function.process_params (D:\Aventyn\ClipCare_v2\node_modules\express\lib\router\index.js:330:12) at next (D:\Aventyn\ClipCare_v2\node_modules\express\lib\router\index.js:271:10) at Function.handle (D:\Aventyn\ClipCare_v2\node_modules\express\lib\router\index.js:176:3) at router (D:\Aventyn\ClipCare_v2\node_modules\express\lib\router\index.js:46:12) at Layer.handle [as handle_request] (D:\Aventyn\ClipCare_v2\node_modules\express\lib\router\layer.js:95:5) at trim_prefix (D:\Aventyn\ClipCare_v2\node_modules\express\lib\router\index.js:312:13) at D:\Aventyn\ClipCare_v2\node_modules\express\lib\router\index.js:280:7 at Function.process_params (D:\Aventyn\ClipCare_v2\node_modules\express\lib\router\index.js:330:12) at next (D:\Aventyn\ClipCare_v2\node_modules\express\lib\router\index.js:271:10) at D:\Aventyn\ClipCare_v2\node_modules\express\lib\router\index.js:618:15

Answer 1

尝试改变:

categoryList.pre('save', function (next) {
  // ...
})

至:

categoryList.schema.pre('save', function (next) {
  // ...
})

.pre() 是 Mongoose 架构的一种方法，而不是模型。