Filtering an array in angular2

问题:

I am looking into how to filter an array of data in Angular2.

I looked into using a custom pipe, but I feel this is not what I am looking for, as it seems more geared towards simple presentation transformations rather then filtering large sets of data.

The array is set out as follows:

getLogs(): Array<Logs> {
        return [
            { id: '1', plate: 'plate1', time: 20 },
            { id: '1', plate: 'plate2', time: 30 },
            { id: '1', plate: 'plate3', time: 30 },
            { id: '2', plate: 'plate4', time: 30 },
            { id: '2', plate: 'plate5', time: 30 },
            { id: '2', plate: 'plate6', time: 30 }
        ];
    }

I want to filter this by id. So when I enter "1" into a search bar, it updates to display the corresponding values.

If there is a method on how to do this, I would love to know!

回答1:

There is no way to do that using a default pipe. Here is the list of supported pipes by default: https://github.com/angular/angular/blob/master/modules/angular2/src/common/pipes/common_pipes.ts.

That said you can easily add a pipe for such use case:

import {Injectable, Pipe} from 'angular2/core';

@Pipe({
    name: 'myfilter'
})
@Injectable()
export class MyFilterPipe implements PipeTransform {
    transform(items: any[], args: any[]): any {
        return items.filter(item => item.id.indexOf(args[0]) !== -1);
    }
}

And use it:

import { MyFilterPipe } from './filter-pipe';
(...)

@Component({
  selector: 'my-component',
  pipes: [ MyFilterPipe ],
  template: `
    <ul>
      <li *ngFor="#element of (elements | myfilter:'123')">(...)</li>
    </ul>
  `
})

Hope it helps you, Thierry

回答2:

I have a similar scenario in one of my samples

<input "(keyup)="navigate($event)" />

<div *ngFor="#row of visibleRows"></div>    

......

navigate($event){
        this.model.navigate($event.keyCode);
        this.visibleRows = this.getVisibleRows();
}

getVisibleRows(){
    return this.model.rows.filter((row) => row.rowIndex >= this.model.start && row.rowIndex < this.model.end);
}

My approach is to recalculate the array on some qualifying event. In my case it's keyup. It may seem convenient to bind to a function or filter, but it's recommended to bind to the array directly instead. This is because the change tracking will get confused since the function/filter will return a new array instance every time change tracking is triggered - regardless of what triggered it.

Here is the full source: https://github.com/thelgevold/angular-2-samples/tree/master/components/spreadsheet

I also have a demo: http://www.syntaxsuccess.com/angular-2-samples/#/demo/spreadsheet