unique

Checks that a list has no duplicate items. With key names, checks that no two objects in the list have the same values of these keys.

Error codes: NOT_UNIQUE_ITEMS, FORMAT_ERROR

Live example · edit rules or inputOpen in playground

rules

{
    tags: 'unique',
    users: { unique: 'id' }
}

{
    tags: 'unique',
    users: { unique: 'id' }
}

input

{
    tags: ['a', 'b', 'a'],
    users: [{ id: 1 }, { id: 2 }]
}

{
    tags: ['a', 'b', 'a'],
    users: [{ id: 1 }, { id: 2 }]
}

Invaliderrors

{
  "tags": "NOT_UNIQUE_ITEMS"
}

The arguments are none, or one or more key names:

{ tags:      'unique' }
{ users:     { unique: 'id' } }
{ addresses: { unique: ['country', 'zip'] } }

Without keys, the items must be primitive values. They are compared as strings, so 1 and "1" are duplicates. Empty items are ignored.
With keys, the items must be objects. Two items are duplicates when all their key values are equal. An item with an empty key value is ignored. A key value that is an object or a list gives FORMAT_ERROR, also when another key of the same item is empty.
Duplicates give NOT_UNIQUE_ITEMS for the whole field.
A value that is not a list, or an item of the wrong type, gives FORMAT_ERROR.

The output is the value unchanged.

unique ​