angular2 access ngModel variable from a directive

问题

I am trying to build a datetime picker directive like the following.
<input [(ngModel)]="date1" datetime-picker date-only />

and date1 is assigned as a Date, e.g., new Date()

When I display this in html, text in input element looks like the following
Thu Jan 01 2015 00:00:00 GMT-0500

I want to display like the following instead
2015-01-01 00:00:00

I want to format date WITHIN a directive using DatePipe instead of showing result from default toString() function.

My question is; "within a directive, how do I access ngModel variable?", e.g., date1, so that I can add toString() method.

If my approach is not right, please advise me.

回答1:

Here is simple and easy way to listen and notify ngModel. I have just demonstrated with jQuery for easy understanding. Practically, it can be anything.

import { Directive, ElementRef } from '@angular/core';
import { NgModel } from '@angular/forms';

@Directive({
    selector: `[ngModel][customDir]`,
    providers: [NgModel]
})
export class CustomDirective {


    constructor(private element: ElementRef, private ngModel: NgModel) {

    }

    ngOnInit() {
        let that = this;
        /* Here you can write custom initialization code */

        /* Listening to the value of ngModel */
        that.ngModel.valueChanges.subscribe(function (value) {
            /* Set any value of your custom control */
            $(that.element.nativeElement).data("newValue",value);
        });

        /* Inform ng model for any new change happened */
        $(that.element.nativeElement).bind("customEvent",function (someNewValue) {
                that.ngModel.update.emit(someNewValue);
            }
        });
    }
}

回答2:

For accessing ngModel, you can simply just have an @Input() in your datetime-picker. And since you are using 2-way data binding, you have to emit the changes you make to ngModel.

@Directive({
  selector:'[date-time-picker]'
})
export class DateTimePicker{
  @Input() ngModel;
  @Output() ngModelChange = new EventEmitter();

  ngOnInit(){
    this.ngModelChange.emit(this.ngModel.toDateString());
  }
}

Check this plunk

---

The better way IMHO, is using the DatePipe

@Component({
  selector: 'my-app',
  directives:[DateTimePicker],
  template: `
      <input (ngModelChange)="myDate = $event" [ngModel]="myDate | date:'short'" datetime-picker  />
  `
})
export class AppComponent {
  myDate = new Date();
}

Check this plunk

回答3:

You can use "keyup" and "this.ngModel.model"

import { Directive, HostListener } from '@angular/core';
import { NgModel } from '@angular/forms';

@Directive({
  selector: '[ngModel][customDir]',
  providers: [NgModel]
})
export class CustomDirective {

  constructor(private ngModel: NgModel) { }

  @HostListener('keyup', ['$event']) onKeyUp(event) {
    let value = this.ngModel.model;
    this.ngModel.update.emit(value);
  }
}

来源：https://stackoverflow.com/questions/37381882/angular2-access-ngmodel-variable-from-a-directive