validating an array of uuids in nestjs swagger body - nestjs

Question

It sounds like a quite simple question but I've been searching for a solution for a very long time now. I want to validate an array of UUIDs in an endpoint.
Like this:
["9322c384-fd8e-4a13-80cd-1cbd1ef95ba8", "986dcaf4-c1ea-4218-b6b4-e4fd95a3c28e"]
I have already successfully implemented it as a JSON object { "id": ["9322c384-fd8e-4a13-80cd-1cbd1ef95ba8", "986dcaf4-c1ea-4218-b6b4-e4fd95a3c28e"]} with the following code:
public getIds(
#Body(ValidationPipe)
uuids: uuidDto
) {
console.log(uuids);
}
import { ApiProperty } from '#nestjs/swagger';
import { IsUUID } from 'class-validator';
export class uuidDto {
#IsUUID('4', { each: true })
#ApiProperty({
type: [String],
example: [
'9322c384-fd8e-4a13-80cd-1cbd1ef95ba8',
'986dcaf4-c1ea-4218-b6b4-e4fd95a3c28e',
],
})
id!: string;
}
But unfortunately I can't customize the function that calls that endpoint. So I need a solution to only validate a array of uuids.

Answer 1

instead of type string , write string[]. like below:
import { ApiProperty } from '#nestjs/swagger';
import { IsUUID } from 'class-validator';
export class uuidDto {
#IsUUID('4', { each: true })
#ApiProperty({
type: string[],
example: [
'9322c384-fd8e-4a13-80cd-1cbd1ef95ba8',
'986dcaf4-c1ea-4218-b6b4-e4fd95a3c28e',
],
})
id!: string[];
}

Answer 2

You can build a custom validation pipe for it:
#Injectable()
export class CustomClassValidatorArrayPipe implements PipeTransform {
constructor(private classValidatorFunction: (any)) {}
transform(value: any[], metadata: ArgumentMetadata) {
const errors = value.reduce((result, value, index) => {
if (!this.classValidatorFunction(value))
result.push(`${value} at index ${index} failed validation`)
return result
}, [])
if (errors.length > 0) {
throw new BadRequestException({
status: HttpStatus.BAD_REQUEST,
message: 'Validation failed',
errors
});
}
return value;
}
}
In your controller:
#Post()
createExample(#Body(new CustomClassValidatorArrayPipe(isUUID)) body: string[]) {
...
}
Ensure to use the lowercase functions from class-validator. It has to be isUUID instead of IsUUID. (This is used for the manual validation with class-validator.)
CustomClassValidatorArrayPipe is build modular. You can validate any other type with it. For example a MongoId: #Body(new CustomClassValidatorArrayPipe(isMongoId)) body: ObjectId[]
Result
If you send this:
POST http://localhost:3000/example
Content-Type: application/json
[
"986dcaf4-c1ea-4218-b6b4-e4fd95a3c28e",
"123",
"test"
]
Server will reply:
{
"status": 400,
"message": "Validation failed",
"errors": [
"123 at index 1 failed validation",
"test at index 2 failed validation"
]
}