猫鼬JobSchema.pre('update'，function(n){n()})引发:TypeError:无法读取未定义的属性'numAsyncPres' [英] Mongoose JobSchema.pre('update', function(n){n()}) throws: TypeError: Cannot read property 'numAsyncPres' of undefined

问题描述

我的猫鼬有这个架构，当我将pre与update一起使用时，会出现此错误.

I have this Schema in mongoose and when I use the pre with update, I get this error.

JobSchema.pre('update', function(n){n()})

完全错误

C:\web\production01_server\node_modules\production\node_modules\mongoose\lib\utils.js:413
        throw err;
              ^
TypeError: Cannot read property 'numAsyncPres' of undefined
    at Model._lazySetupHooks (C:\web\production01_server\node_modules\production\node_modules\mongoose\node_modules\hooks\hooks.js:149:49)
    at Model.pre (C:\web\production01_server\node_modules\production\node_modules\mongoose\node_modules\hooks\hooks.js:113:10)
    at Model.doQueue (C:\web\production01_server\node_modules\production\node_modules\mongoose\lib\document.js:1116:41)
    at Model.Document (C:\web\production01_server\node_modules\production\node_modules\mongoose\lib\document.js:55:8)
    at Model.Model (C:\web\production01_server\node_modules\production\node_modules\mongoose\lib\model.js:26:12)
    at Model.model (C:\web\production01_server\node_modules\production\node_modules\mongoose\lib\model.js:910:11)
    at new Model (C:\web\production01_server\node_modules\production\node_modules\mongoose\lib\connection.js:418:15)
    at cb (C:\web\production01_server\node_modules\production\node_modules\mongoose\lib\query.js:804:16)
    at C:\web\production01_server\node_modules\production\node_modules\mongoose\lib\utils.js:408:16
    at C:\web\production01_server\node_modules\production\node_modules\mongoose\node_modules\mongodb\lib\mongodb\cursor.js:133:9

注意:

• pre(保存"工作
• post('update'不会引发错误，也不起作用

推荐答案

Mongoose 4.0通过查询中间件支持预更新挂钩. http://mongoosejs.com/docs/middleware.html

Mongoose 4.0 supports pre update hooks via Query middleware. http://mongoosejs.com/docs/middleware.html

schema.pre('update', function() {
  console.log(this instanceof mongoose.Query); // true
  this.start = Date.now();
});

schema.post('update', function() {
  console.log(this instanceof mongoose.Query); // true
  console.log('update() took ' + (Date.now() - this.start) + ' millis');
});

注意事项:

"查询中间件与文档中间件的区别在于: 重要方式:在文档中间件中，这是指文档 正在更新.在查询中间件中，猫鼬不一定具有 对要更新的文档的引用，因此此是指查询 对象，而不是要更新的文档."

"Query middleware differs from document middleware in a subtle but important way: in document middleware, this refers to the document being updated. In query middleware, mongoose doesn't necessarily have a reference to the document being updated, so this refers to the query object rather than the document being updated."

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