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[];
}

This will validate each item in post.tags array. The same each: true option also works for Set and Map fields.

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[];
}