FilterRunner

FilterRunner extension works together with FilterBuilder, it converts the input data into whatever you like.

caution

Making custom filters by FilterBuilder and FilterRunner is suitable for advanced users, it gives you low-level access to our compiler. In most cases, you can use Functional Filter instead.

How FilterRunner works

FilterRunner transform function will be called when executing the filters, it'll get the input value and arguments, all we have to do is return a value depends on them.

For example, if we have a template like this:

{{ 'id' | prefix(pre='vulcan') }}

Transform function will be called with these arguments:

public async transform(
  options: FilterRunnerTransformOptions<string>
): Promise<any> {
  options.value; // 'id'
  optoins.args; // {pre: 'vulcan'}
  return `${toptions.args.pre}-${options.value}`
}

FilterRunnerTransformOptions

This is the interface of the argument of transform function, it contains the following properties:

• value: The input value

• args: The input arguments

• context: The context of this request, we can use this class to access compiler features, e.g. add new parameters ...etc.

  info

  We haven't exported the interfaces of the compiler, so you need to cast this object to any type then call the functions directly. Please follow Issue #117.

• metadata: The metadata of this request. e.g. profile name, user attributes ...etc.

Example

info

You can check the demo repository for the full code.

import { FilterRunner, FilterRunnerTransformOptions } from '@vulcan-sql/core';export class PrefixFilterRunner extends FilterRunner {  public filterName = 'prefix';  public async transform(    options: FilterRunnerTransformOptions<string>  ): Promise<any> {    return `${options.args?.pre || 'vulcan'}-${options.value}`;  }}