使用@ViewChild获取输入的.nativeElement将返回'undefined'

Question

我在angular2中创建了以下表单:

import {Component, ElementRef, ViewChild, AfterViewInit} from "angular2/core";
import {Observable} from "rxjs/Rx";
import {ControlGroup, Control, Validators, FormBuilder} from "angular2/common";

@Component({
    selector: "ping-pong",
    template: `
                  <form
                     name="someform"                             [ngFormModel]="form">
                      <div class="form-group">
                          <input                                 
                              id="foobar"                        #foobar="ngForm"   <-- without ="ngForm" everything works fine
                              type="text"                        ngControl="foobar"
                              value=""
                              class="form-control"
                          />
                      </div>
                  </form>
              `,
    styles: [`
                  form {
                      width: 300px;
                  }
              `]
})

export class ChangepswdFormComponent implements AfterViewInit {
    @ViewChild("foobar") foobar: ElementRef;
    private form: ControlGroup;

    public constructor(formBuilder: FormBuilder) {
        this.form = formBuilder.group({
            foobar: [""]
        });
    }

    public ngAfterViewInit(): void {
        console.log(this.foobar.nativeElement);
        //observable doesnt work because nativeelement is undefined
        //Observable.fromEvent(this.foobar.nativeElement, "keyup").subscribe(data => console.log(data));
    }
}

在ngAfterViewInit内部,nativeElement位是未定义的,除非我从#foobar ="ngForm"中删除="ngForm"部分.我通过进行以下调整克服了这个问题:

import {Component, ElementRef, ViewChild, AfterViewInit} from "angular2/core";
import {Observable} from "rxjs/Rx";
import {ControlGroup, Control, Validators, FormBuilder} from "angular2/common";

@Component({
    selector: "ping-pong",
    template: `
                  <form
                     name="someform"                             [ngFormModel]="form">
                      <div class="form-group">
                          <input                                 
                              id="foobar"                        #foobar="ngForm"     #tralala
                              type="text"                        ngControl="foobar"
                              value=""
                              class="form-control"
                          />
                      </div>
                  </form>
              `,
    styles: [`
                  form {
                      width: 300px;
                  }
              `]
})

export class ChangepswdFormComponent implements AfterViewInit {
    @ViewChild("tralala") foobar: ElementRef;
    private form: ControlGroup;

    public constructor(formBuilder: FormBuilder) {
        this.form = formBuilder.group({
            foobar: [""]
        });
    }

    public ngAfterViewInit(): void {
        console.log(this.foobar.nativeElement);
        let keyups = Observable.fromEvent(this.foobar.nativeElement, "keyup");
        keyups.subscribe(data => console.log(data));
    }
}

换句话说,我用一个与ngForm无关的辅助主题标签(#tralala)丰富了输入元素.即使这个解决方案有效,但我感觉不舒服,因为感觉我正在应用一个小黑客.我们应该能够以更优雅/直接的方式通过@ViewChild或通过this.form.controls(或类似的东西)检索文本框的本机元素,而不使用像我使用的那样的变通方法.但我无法弄明白具体如何.

快速附录:如果有任何重要性,我正在使用Angular2 2.0-beta7.

Answer 1

只需添加另一个模板变量

#foobar="ngForm" #foobarElement

@ViewChild("foobarElement") foobar: ElementRef;

随着="ngForm"模板变量得到不同的目的,并且不与工作@ViewChild()

如果您认为这仍然有效,请考虑创建错误报告.