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PipeTransform

一個需要由管道實現的介面,用於執行轉換操作。 Angular 會呼叫它的 transform 方法,並把要繫結的值作為第一個引數傳入,其它引數會依次從第二個引數的位置開始傳入。

An interface that is implemented by pipes in order to perform a transformation. Angular invokes the transform method with the value of a binding as the first argument, and any parameters as the second argument in list form.

      
      interface PipeTransform {
  transform(value: any, ...args: any[]): any
}
    

方法

      
      transform(value: any, ...args: any[]): any
    
引數
value any
args any[]
返回值

any

使用說明

In the following example, TruncatePipe returns the shortened value with an added ellipses.

simple_truncate.ts
      
      /**
 * @license
 * Copyright Google LLC All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */

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

@Pipe({name: 'truncate'})
export class TruncatePipe implements PipeTransform {
  transform(value: any) {
    return value.split(' ').slice(0, 2).join(' ') + '...';
  }
}
    

Invoking {{ 'It was the best of times' | truncate }} in a template will produce It was....

In the following example, TruncatePipe takes parameters that sets the truncated length and the string to append with.

truncate.ts
      
      /**
 * @license
 * Copyright Google LLC All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */

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

@Pipe({name: 'truncate'})
export class TruncatePipe implements PipeTransform {
  transform(value: any, length: number, symbol: string) {
    return value.split(' ').slice(0, length).join(' ') + symbol;
  }
}
    

在範本中呼叫 {{ 'ok' | repeat:3 }} 的結果是 okokok

Invoking {{ 'It was the best of times' | truncate:4:'....' }} in a template will produce It was the best.....