Validating plain objects using a class with decorators?

The document says plain objects can be validated using a ValidationSchema, so I think it is possible to enhance the validate to accept a class with decorators to valid plain objects?

For example:

export interface RegisterUserArgs {
    username: string;
}

export class RegisterUserArgsSchema implements RegisterUserArgs {
    @MinLength(6)
    username: string;
}

const args = { username: 'Whoami' }
validate(RegisterUserArgsSchema, args).then(/*...*/); 

Comparing to ValidationSchema, define a schema class avoids typos.

I know there is a class-transform-validator package, but it actually validates a new transformed object and thus may leads to additional complexity and performance issues.

[Yaojian]

How about write a Custom Validator, such as ValidateNestedAs(Outer) ?

for example

class Outer {
    @ValidateNestedAs(Inner)
    inner: Inner;
}

[MichalLytek]

Of course, you need instances for each class or array. That’s why I recommend using class-transformer that has covered all edge cases.