如何在Json文件中搜索和匹配2个输入字段值，如果找到匹配项，则从同一json对象返回第3个键值

Question

我有2个输入字段，用户将在其中输入取件和交货区域名称。当用户完成第二次输入（交货或取件-无序列）时，我想启动一个过程，从JSON文件中搜索两个输入值，如果匹配对于这两个输入，找到相关的价格。 我能够捕获两个输入中的值，但是我需要一种方法将它们与JSON文件进行比较，并在成功显示比赛价格时进行比较。 在构造函数中定义的方法，为我提供了Json文件中的所有对象。

注意。 查找匹配过程不会以单击开始，而是以（更改）值开始。

模板

<div class="form-group">
  <input class="form-control" id="pickupSuburb" (change)="onSelectedSuburb($event)" placeholder=" Pickup Suburb Here"   [(ngModel)]="pickupSuburb"  >
</div>

<div class="form-group">
  <input list="suburb" class="form-control" id="deliverySuburb" (change)="onSelectedSuburb($event)" placeholder=" Delivery Suburb Here" [(ngModel)]="deliverySuburb" >
</div>

零件

import {Component, OnInit, ElementRef } from '@angular/core';
import 'rxjs/add/operator/map'
import { FormControl } from '@angular/forms';
import {Http} from '@angular/http';

@Component({
  selector: 'app-sending',
  templateUrl: './sending.component.html',
  styleUrls: ['./sending.component.css'],
  providers: [SuburbsService, AutoCompleteSuburbs, CapitalizePipe ],
})

export class SendingComponent implements OnInit {
  priceList = [];

  constructor(private elm: ElementRef, private http: Http) {
    http.get('./assets/zoneRates.json').subscribe(response => {
      this.priceList = response.json();
    })
  }

  ngOnInit () {}

  public onSelectedSuburb(event) {
    const pickupArray = this.elm.nativeElement.querySelector('#pickupSuburb').value.slice(1).slice(-3);
    const deliveryArray = this.elm.nativeElement.querySelector('#deliverySuburb').value.slice(1).slice(-3);}

杰森样品

[{
    "pickup": "SYD",
    "delivery": "QC4",
    "weight": "25",
    "price": "6.25"
  }, {
    "pickup": "SYD",
    "delivery": "QC6",
    "weight": "25",
    "price": "6.25"
  }, {
    "pickup": "SYD",
    "delivery": "QC7",
    "weight": "25",
    "price": "6.25"
  }, {
    "pickup": "SYD",
    "delivery": "ADL",
    "weight": "25",
    "price": "6.25"
  }]

Answer 1

您可以使用OnChanges生命周期挂钩，并使用array.prototype.find搜索产品数组。 我在任何地方都看不到您声明该表单，因此我假设您使用的是反应式表单。 我建议切换到动态表单（ https://angular.io/guide/dynamic-form ），因为这将使获取值更加容易。

我的答案是假设您进行此开关并在组件中声明了pickupInput和deliveryAreaInput属性，这些属性绑定到表单上的关联输入。 如果您需要坚持使用reactForms，则必须以其他方式获取这些值。

export class sendingComponent implements onChanges, onInit {
  private pickupInput: FormControl = new FormControl('', Validators.required); // You may need different validation than this.
  private deliveryAreaInput: FormControl = new FormControl('', Validators.required); // again your validation may differ.

  /**
   * Checks if either pickupInput or deliveryAreaInput are in the changes object.
   * If either key is included pass both values to the searchJson method and store the response in a match property
   * If match is truthy show the price
   * @param {SimpleChanges} changes
   */ 
  ngOnChanges(changes: SimpleChanges) {
    if (changes.pickupInput || changes.delieveryAreaInput) {
      const match: any = this.searchJson(this.pickupInput.value, this.deliveryAreaInput.value);
      if (match) {
        this.showPrice = true; // Use this with an ngIf in your template
      }
    }
  }

  /**
   * Use Array.prototype.find to search through the priceList array for any products that have a matching pickup and delivery area.
   * Array.prototype.find returns either the matching value or undefined if no matches are found.
   * @param {string} pickup
   * @param {string} deliveryArea
   * @return {?} either the matching value or undefined
   */
  private searchJson(pickUp: string, deliveryArea: string): any {
    return this.priceList.find(price => {
      return price.pickup === pickUp && price.delivery === deliveryArea;
    });
  }
}

不过，我会担心对变更进行搜索。 这将导致在每次按键时搜索整个产品目录，如果目录较长，则会明显变慢。 更好的解决方案是引入一个按钮或搜索焦点而不是更改（尽管这将要求用户明显地聚焦）。