ngForIn能用于angular 4吗？

Question

我试图使用*ngfor迭代对象的属性，但在中使用。当我试着这么做的时候

@Controller({
  selector: 'sample-controller',
  template: `
    <ul>
      <li *ngFor="let i in obj">
        <b>{{i}}</b>: {{obj[i]}}
      </li>
    </ul>`
})
class SampleController {
  obj = {a: 1, b: 2}
}




Answer 1

正如注释中提到的AJT_82，您可以为此目的创建特殊指令。它将基于ngforof 指令：

interface NgForInChanges extends SimpleChanges {
  ngForIn?: SimpleChange;
  ngForOf?: SimpleChange;
}

@Directive({
  selector: '[ngFor][ngForIn]'
})
export class NgForIn<T> extends NgForOf<T> implements OnChanges {

  @Input() ngForIn: any;

  ngOnChanges(changes: NgForInChanges): void {
    if (changes.ngForIn) {
      this.ngForOf = Object.keys(this.ngForIn) as Array<any>;

      const change = changes.ngForIn;
      const currentValue = Object.keys(change.currentValue);
      const previousValue = change.previousValue ? 
                            Object.keys(change.previousValue) : undefined;
      changes.ngForOf =  new SimpleChange(previousValue, currentValue, change.firstChange);

      super.ngOnChanges(changes);
    }
  }
}

柱塞示例