Class-transformer: [bug/proposal] for boolean prop type and enabled `enableImplicitConversion` flag

Created on 4 Nov 2019 · 13Comments · Source: typestack/class-transformer

version: "class-transformer": "0.2.3"

example:

import 'reflect-metadata';
import { Expose, plainToClass } from 'class-transformer';

class TestClass {
    @Expose()
    prop: boolean;
}

console.log(plainToClass(TestClass, {
    prop: 'false',
}, {
    enableImplicitConversion: true,
}));

returned: TestClass { prop: true }
expected: TestClass { prop: false }

proposal:
if value === 'true' || value === true || value === 1 || value === '1' then true
otherwise false

somethink like ths:

import { Transform } from 'class-transformer';

export function ToBoolean(): (target: any, key: string) => void {
    return Transform((value: any) => value === 'true' || value === true || value === 1 || value === '1');
}

duplicate feature

Source

ruscon

👍15 😕1

Most helpful comment

The shortest version I can think of

import { Transform } from "class-transformer";

export function ToBoolean() {
    return Transform(v => ["1", 1, "true", true].includes(v));
}

numToStr on 15 Apr 2020

👍4 👎1

All 13 comments

Looks like we have the same issue.
see my SOF question

joeloudjinz on 26 Nov 2019

This issue also means @IsBoolean is useless since any value can be transformed to a boolean.

dsbert on 7 Jan 2020

👍1

Since this is still open, is there any work around?

adzamkomladev on 9 Jan 2020

@adzamkomladev I'm still waiting for an answer from the developer on how it should work

ruscon on 9 Jan 2020

👍1

same problem here

leepood on 11 Mar 2020

👍1

This issue also means @IsBoolean is useless since any value can be transformed to a boolean.

Until the issue gets fixed, I'm using this approach to handle it:

// ...

@IsBoolean()
@Transform(it => {
  switch (it) {
    case 'true':
      return true;
    case 'false':
      return false;
    default:
      return it;
  }
})
verified!: boolean;

// ...

mostafa-hz on 6 Apr 2020

👍1

Same problem here... I have a DTO with a boolean type on it, but I can't actually treat it like a boolean because at runtime it has type string everywhere...

karam94 on 10 Apr 2020

The shortest version I can think of

import { Transform } from "class-transformer";

export function ToBoolean() {
    return Transform(v => ["1", 1, "true", true].includes(v));
}

numToStr on 15 Apr 2020

👍4 👎1

@numToStr I think this is rather misguided as it will convert all objects not in the set ["1", 1, "true", true] to false. I think this is far too broad a definition for type coercion.

DanielLoyAugmedix on 26 Jun 2020

👍1

Hi all!

You can see some comments about this on #334 and #363. In short Boolean('false') == true so the library behaves as expected. We still need some discussion about the correct approach, most probably we will add a custom flag for this.