multitest_transport/ui2/app/shared/map_list_field_pipe.ts

/**
 * Copyright 2019 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import {Pipe, PipeTransform} from '@angular/core';


/**
 * Maps a list of objects to a given field for each object.
 *
 * Example: Given a list of Tests with a 'name' field, it will return a list of
 * the names
 */
@Pipe({name: 'mapListField'})
export class MapListFieldPipe implements PipeTransform {
  transform<T>(list: T[]|null, field: keyof T, allowDuplicates = false):
      Array<T[keyof T]> {
    if (!list) {
      return [];
    }
    const fieldList = list.map(val => val[field]);
    if (allowDuplicates) {
      return fieldList;
    } else {
      return Array.from(new Set(fieldList));
    }
  }
}