How to pass function as arg Pipe angular2

Question

I'd like to have a generic fields filter that will get the filter function as an argument and use it in filter

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

@Pipe({
  name: 'FieldsFilter'
})
@Injectable()
export class FieldsFilter implements PipeTransform {
  transform(fields: any[], args: any[]): any {
    return fields.filter(args[0]);//pass function to filter
  }
}

So I could use it in multiple places with different filter functions.

How do I pass the filter function?

Isagoge

Answer 1

@Pipe({
  name: 'FieldsFilter'
})
@Injectable()
export class FieldsFilter implements PipeTransform {
  transform(fields: any[], f): any {
    return fields.filter((e) => f(e));
  }
}

it was changed quite a while ago that additional pipe parameters are passed to individual parameters instead of as single parameter in the form of an array.

Labors

I get an error when trying to refer to this in the argument function. how do I bind it? – Isagoge

I see. Assign the function to a field in the compinent like this.f = this.filterFuntion.bind(this); and then pass f to the pipe. – Barbule

The advantage IMHO of .bind(this) is that it doesn't matter how many parameters the method supports, with => you need (a, b, c) => myFunc(a, b, c). I favor => for inline functions though. – Barbule

@GünterZöchbauer thanks! but how can i use it as a filter for ngFor meaning to say that it should be to bind it to a prop and it should be invoked every time it changes? – Boldt

@JoeB it might be bettet to create a new question with some code that demonstrates what you try to accomplish. I don't get what the problem is from your comment. – Barbule

@GünterZöchbauer Thanks i posted a new question #45722983 – Boldt