PipeTransform
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
}
Methods
transform() |
---|
Usage notes
In the following example, TruncatePipe
returns the shortened value with an added ellipses.
import {Pipe, PipeTransform} from '@angular/core';
@Pipe({name: 'truncate'})
export class TruncatePipe implements PipeTransform {
transform(value: string) {
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.
import {Pipe, PipeTransform} from '@angular/core';
@Pipe({name: 'truncate'})
export class TruncatePipe implements PipeTransform {
transform(value: string, length: number, symbol: string) {
return value.split(' ').slice(0, length).join(' ') + symbol;
}
}
Invoking {{ 'It was the best of times' | truncate:4:'....' }}
in a template will produce It was the best....
.