Angular - pass pipe as variable

Question

How may I store and use pipe information from variables?

I've already searched a lot but couldn't find a solution for that.

What I'm trying to achieve is passing any valid pipe information as a variable (decimal, percent, date, custom, etc). Follows a simple example:

parent.component.ts:

columnsDef = {
  value: 0.35,
  pipeInfo: 'percent:"0.2-2":"pt-BR"'
};

parent.component html:

<app-display-component [columnsDef]="columnsDef"></app-display-component>

app-display.component html:

<h1> {{ columnsDef.value | columnsDef.pipeInfo }}</h1>

The expected output is the value formatted as a percentage, but all I get is a template parse error:

ERROR Error: Uncaught (in promise): Error: Template parse errors: Parser Error: Unexpected token '.'

Answer 1

You can create a custom pipe which gets another pipe as an argument and apply it to the value given to it.

Here is an example of a dynamic pipe created by @balu in this answer. See the link for more info.

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


@Pipe({
  name: 'dynamicPipe'
})
export class DynamicPipe implements PipeTransform {

    public constructor(private injector: Injector) {
    }

    transform(value: any, pipeToken: any, pipeArgs: any[]): any {
        if (!pipeToken) {
            return value;
        }
        else {
            let pipe = this.injector.get(pipeToken);
            return pipe.transform(value, ...pipeArgs);
        }
    }
}