Validating Arrays

Basic Array Validation

If your field is an array and you want to perform validation of each item in the array, you must specify a special each: true decorator option:

import { MaxLength } from 'class-validator';

export class Post {
    @MaxLength(20, {
        each: true,
    })
    tags: string[];
}

Array-specific Decorators

There are also several decorators specifically for array validation:

Decorator	Description
@ArrayContains(values: any[])	Checks if array contains all values from the given array of values.
@ArrayNotContains(values: any[])	Checks if array does not contain any of the given values.
@ArrayNotEmpty()	Checks if given array is not empty.
@ArrayMinSize(min: number)	Checks if array's length is greater than or equal to the specified number.
@ArrayMaxSize(max: number)	Checks if array's length is less or equal to the specified number.
@ArrayUnique()	Checks if all array's values are unique.

Example:

import { ArrayMinSize, ArrayMaxSize, ArrayUnique } from 'class-validator';

export class Post {
    @ArrayMinSize(1)
    @ArrayMaxSize(10)
    @ArrayUnique()
    tags: string[];
}