Validation on optional Parameter using class-validator in nestjs?

Question

I want to apply validation on request payload like, there is field name with string type. But name is not compulsory field but if it exist it must execute @IsNotEmpty()

I tried something like this @IsNotEmpty() name?: string // it not considering ? optional constraint

Answer 1

You can use the @IsOptional() validator:

Checks if given value is empty (=== null, === undefined) and if so, ignores all the validators on the property.

Answer 2

class-validator has an @IsOptional() validator that you can add on along with any other validators you defined like so:

@IsOptional() @IsNotEmpty() name: string;

The decorators are commutative so validation doesn't depend on the order of the validators. If the need to validate depends on something other than presence, you can use @ValidateIf() which takes a function argument.

Answer 3

Kim's answer is great. If you want to apply this behavior to all of your optional fields, you can also use skipMissingProperties: true with your validation pipe(s).