Question

我正在尝试将具有res.send（）的人员对象从快速后端发送回有角度的前端，但是res.send（）始终发送空对象。我正在使用cors将数据从localhost / 8081的express后端发送到localhost / 4200的有角前端。

表达后端

controller.js

controller.getPerson = async (req, res) => {
   try{
      console.log(req.body);
      var result = await service.getPerson(req.body._id));
      console.log(result);
      res.send(result); <--- sending undefined object or nothing at all instead of result
   } 
   catch(error)
   {
        console.log("controller/get_person)", error)
   }
};

service.js

service.getPerson = (data) =>{;
       return Person.findById({'_id':data}, function(err, docs){
        console.log(docs);
            return docs;
      });
    };

输出

{ _id: '5f126357aea7624680d07ee2' } <-- console.log(req.body)
console.log(docs)
{
  _id: 5f126357aea7624680d07ee2,
  first_name: 'qwer',
  last_name: 'qwer',
  __v: 0
}
console.log(result)
{
  _id: 5f126357aea7624680d07ee2,
  first_name: 'qwer',
  last_name: 'qwer',
  __v: 0
}

console.log（req.body）返回{_id：'someid'}，console.log（docs）返回带有id的整个人员对象，console.log（result）显示与console相同的内容.log（docs）

角形前端

person-detail.component

  @Input() person: Person;
  getPerson(): void {
    const id = this.route.snapshot.paramMap.get('id');
    this.personService.getPerson(id)
    .subscribe(person => this.person = person); <-- this.person is not set because person is undefined or doesn't exist
  }

person.service

  public getPerson(_id){
        return this.http.post<Person>('http://localhost:8081/get_person', {_id});
  }

前端角度错误

core.js:4081 ERROR Error: NodeInjector: NOT_FOUND [NgControl]
at getOrCreateInjectable (core.js:3819)
at Module.ɵɵdirectiveInject (core.js:13733)
at NodeInjectorFactory.NgControlStatus_Factory [as factory] (forms.js:677)
at getNodeInjectable (core.js:3913)
at instantiateAllDirectives (core.js:7973)
at createDirectivesInstances (core.js:7356)
at Module.ɵɵelementStart (core.js:13882)
at PersonDetailComponent_div_0_Template (person-detail.component.html:6)
at executeTemplate (core.js:7329)
at renderView (core.js:7138)

personService.getPerson（id）未获取person对象，因此person始终为空对象。如何解决这个问题，以便person => this.person = person使得this.person成为通过res.send（）发送回去的person对象？

Answer 1

您没有在服务函数中等待回调函数。

将其包装在承诺中或为findById使用相应的承诺。

service.getPerson = (data) => {
       return new Promise(resolve => { 
           Person.findById({'_id':data}, function(err, docs){
             console.log(docs);
             resolve(docs);
           });
       });
};

编辑。有一个built in promise support by mongoose。

res.send（）发送空对象

1 个答案: