PipeTransform
一个需要由管道实现的接口，用于执行转换操作。 Angular 会调用它的 transform 方法，并把要绑定的值作为第一个参数传入，其它参数会依次从第二个参数的位置开始传入。
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
使用说明
In the following example, TruncatePipe returns the shortened value with an added ellipses.
/**
* @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.
/**
* @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;
}
}
在模板中调用 {{ 'ok' | repeat:3 }} 的结果是 okokok。
Invoking {{ 'It was the best of times' | truncate:4:'....' }} in a template will produce It was the best.....
