angular2实现一个管道，根据选定的属性对数组对象进行排序

Question

I have an array of products:

public sort_criteria: any='';

public products: any = [
{title: 'Product_1', desc: 'Lorem Ipsum is simply dummy text of the printing and typesetting industry', img: '../assets/prod_1.jpg', property_1: 50, property_2: 6, property_3: 0, property_4: 76, property_5: 54, property_6: 87, property_7: 0},
{title: 'Product_2', desc: 'Lorem Ipsum has been the industrys standard dummy text ever since the 1500s', img: '../assets/prod_2.jpg', property_1: 0, property_2: 0, property_3: 65, property_4: 0, property_5: 0, property_6: 7, property_7: 88},
{title: 'Product_3', desc: 'It has survived not only five centuries but also the leap into electronic typesetting', img: '../assets/prod_3.jpg', property_1: 0, property_2: 97, property_3: 0, property_4: 56, property_5: 0, property_6: 0, property_7: 86},
{title: 'Product_4', desc: ' It was popularised in the 1960s with the release of Letraset sheets containing,', img: '../assets/prod_4.jpg', property_1: 90, property_2: 25, property_3: 56, property_4: 64, property_5: 0, property_6: 98, property_7: 0},
]

public sort_according_to: any=['Product 1', 'Product 2', 'Product 3', 'Product 4']

setSortCriteria(criteria){

    switch (criteria) {
        case "Product 1":
        alert(3)
        break;
        case "Product 2":
        alert(2)
        break;
        case "Product 3":
        alert(3)
        break;
        case "Product 4":
        alert(4)
        break;      
        default:
        break;
    }
}

My user will select one of the properties from 7 properties and whatever property he selects my products should be sorted in descending oder of that property ie if he selects Property 1 then my sequence of my products will be 4,1,2,3.

My HTML:

  <h5>Sort products according to the popularity of</h5>

  <div *ngFor="let product of sort_according_to">
    <mdl-radio name="productgroup" [value]='product' [(ngModel)]="sort_criteria" (change)="setSortCriteria(product)"> {{product}} </mdl-radio>
  </div>


  <mdl-card *ngFor="let product of products" class="demo-card-square" mdl-shadow="2">
    <figure class="mdl-card__media">
      <img src="{{product.img}}" alt="" />
    </figure>
    <mdl-card-title mdl-card-expand>
      <h2 mdl-card-title-text>{{product.title}}</h2><br>
    </mdl-card-title>

    <mdl-card-supporting-text>
      {{product.desc}}
    </mdl-card-supporting-text>
    <mdl-card-actions mdl-card-border>
      <button mdl-button mdl-colored mdl-ripple (click)="openProductDetails()">
        view
      </button>
      <div class="mdl-layout-spacer"></div>
      <button class="mdl-button mdl-button--icon mdl-button--colored" (click)="addToCart(product)"><i class="material-icons">shopping_cart</i></button>
    </mdl-card-actions>
  </mdl-card>

How can I implement a pipe in that case?

Answer 1

You can pass the array & a sorting property into a pipe. The pipe can then sort the array by that property.

// component.html
<mdl-card *ngFor="let product of products | sortArrayByProperty : sort_criteria">
</mdl-card>

//pipe.ts
@Pipe({
    name: 'sortArrayByProperty'
})
export class SortArrayByPropertyPipe implements PipeTransform {
    transform(arr: any[]: property: string): any[] {
        // basic sort by property method
        return arr.sort((a, b) => b[property] - a[property]);
    }
}

Here is a basic working plnkr https://plnkr.co/edit/XgzkljALx2cEHWLSGOTs?p=preview