Angular 获取co.myFunction不是函数错误

我在执行angularjs代码时遇到以下错误 HTML代码：

<tbody>
              <tr>
              <td class=" ">1<sup>st</sup>
                <div class="box draggable" 
                      appDraggable
                      (draggStart)="ondraggStart()">Delete1</div></td>
                <td class=""><button class="btn " data-toggle="modal" data-target="#EditClass">Edit</button>
                <button class="btn  ">Delete</button></td>
              </tr>
              <tr>
              <td class=" ">2<sup>nd</sup></td>
                <td class=""><button class="btn " data-toggle="modal" data-target="#EditClass">Edit</button>
                <button class="btn  ">Delete</button></td>
              </tr>
              <tr>
              <td class=" ">3<sup>rd</sup></td>
                <td class=""><button class="btn " data-toggle="modal" data-target="#EditClass">Edit</button>
                <button class="btn  ">Delete</button></td>
              </tr>

            </tbody>

下面是我的 draggble.directive.ts代码：

import { Directive, HostBinding, HostListener, Output, EventEmitter } from 
'@angular/core';
@Directive({
selector: '[appDraggable]'})
export class DraggableDirective {
@HostBinding('class.draggable') draggable=true;
@Output() draggStart =new EventEmitter<PointerEvent>();
private dragging =false;
@HostListener('pointerdown',['$event']) onpointerdown(event:PointerEvent): 
void{
  this.dragging=true;
  this.draggStart.emit(event);
}
}

---

如果有人在angular project中遇到此错误，请告诉我，通过加载引导库，我的问题已得到解决。

可能是

co.ondragStart

中的输入错误。为了进一步帮助您，我们需要查看实际的html和ts。这里没有太多信息。但是如果“ondragStart”应该是一个内置的UI事件，那么也许可以将“d”大写，看看这是否解决了问题。

import { Directive, HostBinding, HostListener, Output, EventEmitter } from 
'@angular/core';
@Directive({
selector: '[appDraggable]'})
export class DraggableDirective {
@HostBinding('class.draggable') draggable=true;
@Output() draggStart =new EventEmitter<PointerEvent>();
private dragging =false;
@HostListener('pointerdown',['$event']) onpointerdown(event:PointerEvent): 
void{
  this.dragging=true;
  this.draggStart.emit(event);
}
}

ERROR TypeError: _co.ondraggStart is not a function
at Object.eval [as handleEvent] (AddClassComponent.html:24)
at handleEvent (core.js:10251)