angular - 如何停止在 Angular 垫片中添加新值和重复值？

Question

我正在使用 angular 9 mat-chips，我想知道如何停止在输入中添加新值，只允许添加自动完成列表中的项目，即输入不在列表中的“abc”自动完成列表并按回车键会在输入中添加“abc 作为芯片”，需要避免只添加自动完成列表中的值。另外，我想知道如何停止在 Angular 垫片中添加重复项，即如果我已经添加了柠檬柠檬，则不应将其添加到垫片列表中，并且也应从自动完成列表中删除。

以下是代码:

chip-autocomplete.component.ts

@Component({
  selector: 'chips-autocomplete-example',
  templateUrl: 'chips-autocomplete-example.html',
  styleUrls: ['chips-autocomplete-example.css'],
})

export class ChipsAutocompleteExample {
  visible = true;
  selectable = true;
  removable = true;
  separatorKeysCodes: number[] = [ENTER, COMMA];
  fruitCtrl = new FormControl();
  filteredFruits: Observable<string[]>;
  fruits: string[] = ['Lemon'];
  allFruits: string[] = ['Apple', 'Lemon', 'Lime', 'Orange', 'Strawberry'];

  @ViewChild('fruitInput') fruitInput: ElementRef<HTMLInputElement>;
  @ViewChild('auto') matAutocomplete: MatAutocomplete;

  constructor() {
    this.filteredFruits = this.fruitCtrl.valueChanges.pipe(
        startWith(null),
        map((fruit: string | null) => fruit ? this._filter(fruit) : this.allFruits.slice()));
  }

  add(event: MatChipInputEvent): void {
    const input = event.input;
    const value = event.value;

    // Add our fruit
    if ((value || '').trim()) {
      this.fruits.push(value.trim());
    }

    // Reset the input value
    if (input) {
      input.value = '';
    }

    this.fruitCtrl.setValue(null);
  }

  remove(fruit: string): void {
    const index = this.fruits.indexOf(fruit);

    if (index >= 0) {
      this.fruits.splice(index, 1);
    }
  }

  selected(event: MatAutocompleteSelectedEvent): void {
    this.fruits.push(event.option.viewValue);
    this.fruitInput.nativeElement.value = '';
    this.fruitCtrl.setValue(null);
  }

  private _filter(value: string): string[] {
    const filterValue = value.toLowerCase();

    return this.allFruits.filter(fruit => fruit.toLowerCase().indexOf(filterValue) === 0);
  }
}

chip-autocomplete.component.html

<mat-form-field class="example-chip-list">
  <mat-chip-list #chipList aria-label="Fruit selection">
    <mat-chip
      *ngFor="let fruit of fruits"
      [selectable]="selectable"
      [removable]="removable"
      (removed)="remove(fruit)">
      {{fruit}}
      <mat-icon matChipRemove *ngIf="removable">cancel</mat-icon>
    </mat-chip>
    <input
      placeholder="New fruit..."
      #fruitInput
      [formControl]="fruitCtrl"
      [matAutocomplete]="auto"
      [matChipInputFor]="chipList"
      [matChipInputSeparatorKeyCodes]="separatorKeysCodes"
      (matChipInputTokenEnd)="add($event)">
  </mat-chip-list>
  <mat-autocomplete #auto="matAutocomplete" (optionSelected)="selected($event)">
    <mat-option *ngFor="let fruit of filteredFruits | async" [value]="fruit">
      {{fruit}}
    </mat-option>
  </mat-autocomplete>
</mat-form-field>

app.component.html

<div class="mat-app-background basic-container">
  <chips-autocomplete-example>loading</chips-autocomplete-example>
</div>

可以在以下位置找到类似于此代码的堆栈 Blitz (来自 Angular Material Design):https://stackblitz.com/angular/gdjdrkxaedv?file=src%2Fapp%2Fchips-autocomplete-example.ts

Answer 1

您可以添加过滤方法来删除下拉列表中的重复条目。

getUniqueList(fruitList: string[]) {
  return fruitList.filter(x => this.fruits.indexOf(x) === -1);
}

以及你的构造函数的所有过滤方法。

constructor() {
this.filteredFruits = this.fruitCtrl.valueChanges.pipe(
  startWith(null),
  map((fruit: string | null) =>
    fruit
      ? this.getUniqueList(this._filter(fruit))
      : this.getUniqueList(this.allFruits.slice())
  )
);
}

然后为 remove 方法添加更新

remove(fruit: string): void {
const index = this.fruits.indexOf(fruit);

if (index >= 0) {
  this.fruits.splice(index, 1);
}
this.fruitCtrl.updateValueAndValidity();
}

要添加独特的项目，您可以使用以下代码。

// Add our fruit
if ((value || "").trim()) {
  const filterList = this.getUniqueList(this.allFruits);
  const index = filterList.indexOf(event.value);
  if (index > -1) {
    this.fruits.push(value.trim());
  }
}

您可以引用更新后的代码 here.