Conditional Validation

The conditional validation decorator (@ValidateIf) can be used to ignore the validators on a property when the provided condition function returns false.

Basic Usage

import { ValidateIf, IsNotEmpty } from 'class-validator';

export class Post {
    otherProperty: string;

    @ValidateIf(o => o.otherProperty === 'value')
    @IsNotEmpty()
    example: string;
}

In this example, the validation rules applied to example won't be run unless the object's otherProperty is "value".

Important Notes

1. When the condition is false, all validation decorators are ignored
2. The condition function takes the object being validated as a parameter
3. The condition function must return a boolean
4. Multiple @ValidateIf decorators can be used on the same property

Advanced Example

import { ValidateIf, IsNotEmpty, IsString } from 'class-validator';

export class User {
    @IsString()
    type: string;

    @ValidateIf(o => o.type === 'admin')
    @IsNotEmpty()
    adminKey: string;

    @ValidateIf(o => o.type === 'user')
    @IsNotEmpty()
    userKey: string;
}