从角度控制器调用异步功能

Question

我想从角度表单模板控制器调用异步函数。但是，如果我这样做，执行就会挂起。

跟随html模板：

<div class="container">
    <form>
      <div class="form-group">
        <label for="address">Identnummer (Adresse)&nbsp;*</label>
        <input type="text" class="form-control" id="address" required placeholder="0x"
                    [(ngModel)]="model.address"
                    #address="ngForm"
                    [ngClass]="setAddressCssValidityClass(address)"
                    ngControl="address">
      </div>

      <div class="row">
        <div class="col-auto">
          <button type="submit" class="btn btn-primary">Submit</button>
        </div>
        <small class="col text-right">*&nbsp;Required</small>
      </div>
    </form>
  </div>

这是我的控制器的简化版：

import 'package:angular/angular.dart';
import 'package:angular_forms/angular_forms.dart';

@Component(
  selector: 'sCert-validate-form',
  templateUrl: 'sCert_validate_form_component.html',
  directives: [coreDirectives, formDirectives],
)
class ScertValidateFormComponent {

  Map<String, bool> setAddressCssValidityClass(NgControl control) {
    var validityClass;
    //callCertificateByAddress(control.value);
    if(control.value == "test"){
      validityClass = 'is-valid';
      callCertificateByAddress(control.value);      
    }
    else{
      validityClass = 'is-invalid';
    }
    Map<String, bool> map = {validityClass: true};
    return map;
  }

  Future<bool> callCertificateByAddress(String address) async {
    // some code -> also does not work if removed
    return true;
  }
}

Future<bool> callCertificateByAddress(String address) async必须是异步的，因为我在那里进行了异步lib调用。但是如何结合模板来实现呢？

Answer 1

只使用这样的异步管道

 [ngClass]="setAddressCssValidityClass(address) | async"

Answer 2

存在问题：您将回调绑定到此处的输入[ngClass]="setAddressCssValidityClass(address)"在每个更改检测周期中，角度调用函数[将调用网络]。并且来自http的响应会强制执行新的更改检测，该检测会递归地一次又一次地调用http。将结果保存到某个变量，然后将其绑定到ngClass而不是方法上。

ngOnInit() {
  this.classes = this.setAddressCssValidityClass(address);
}
....
[ngClass]="classes"