Transform and IsInt for arrays are not working

[unkindypie]

DTO:

export class RegisterAccountDto {
   ...

  @ApiProperty({ type: [Number] })
  @Transform(({ value }) => {
    return Number(value);
  })
  @IsInt({ each: true })
  expertiseKeywordIds: number[];

}

Payload:

Route handler gets this value:

expertiseKeywordIds: 1

Without any decorators everything works although I need to parse and validate array manually. IsInt without Transform have the same bug.

[dmitriy-nz]

Hi, the problem is that you transform the array of strings into a number. @Transform decorator is not called for every value of the array, but only for the entire array.

[dmitriy-nz]

Please read the documentation for class-transformer You can use this decorator to convert an array of strings to an array of numbers

//ToNumber.ts
export function toNumber(value: any) {
  const res: number = +value;
  return (isNaN(res)) ? null : res;
}

export function ToNumber(): (target: any, key: string) => void {
  return Transform((params: TransformFnParams) => toNumber(params.value));
}

//ToArrayNumber.ts
export function toArrayNumber(v: any[]): number[] {
  return (Array.isArray(v))
    ? v.map(v => toNumber(v))
    : null;
}

export function ToArrayNumber(): (target: any, key: string) => void {
  return Transform((params: TransformFnParams) => toArrayNumber(params.value));
}

[unkindypie]

My bad, thank you for the explanation.