enum : Array<Any>
enum
Array<Any>Validation succeeds if the instance is equal to one of the elements in this keyword’s array value.
| Value | This keyword must be set to a non-empty array of unique JSON values |
|---|---|
| Kind | Assertion |
| Applies To | Any |
| Base Dialect | 2020-12 |
| Changed In | None |
| Introduced In | Draft 1 |
| Vocabulary | Validation |
| Specification | https://json-schema.org/draft/2020-12/json-schema-validation.html#section-6.1.2 |
| Metaschema | https://json-schema.org/draft/2020-12/meta/validation |
| Official Tests | draft2020-12/enum.json |
| Default | None |
| Annotation | None |
| Affected By | None |
| Affects | None |
| Also See |
|
The enum keyword restricts instances to a finite set of possible values,
which may be of different types.
Best Practice
Constraining instances to a set of possible values by definition implies the given JSON types. Therefore, combining this keyword with the
type keyword is redundant (or
even invalid if types don’t agree), and considered an
anti-pattern.
Common Pitfall
There are programming languages, such as JavaScript, that cannot distinguish between integers and real numbers. To accomodate for those cases, JSON Schema considers a real number with a zero fractional part to be equal to the corresponding integer. For example, in JSON Schema,
1 is
considered to be equal to 1.0.
Examples
A schema that constrains instances to an homogeneous string enumeration
Schema
{
"$schema": "https://json-schema.org/draft/2020-12/schema",
"enum": [ "red", "green", "blue" ]
}
Valid
A string value that equals a value in the enumeration is valid
Instance
"green"
Invalid
A string value that does not equal a value in the enumeration is invalid
Instance
"black"
Invalid
Any other value is invalid
Instance
2
A schema that constrains instances to an homogeneous numeric enumeration
Schema
{
"$schema": "https://json-schema.org/draft/2020-12/schema",
"enum": [ 1, 2.0, 3 ]
}
Valid
An integer value that equals a value in the enumeration is valid
Instance
1
Valid
An integer representation of a real value that equals a value in the enumeration is valid
Instance
2
Invalid
Any other number value is invalid
Instance
5
Invalid
Any other non-number value is invalid
Instance
"Hello"
A schema that constrains instances to an heterogeneous enumeration
Schema
{
"$schema": "https://json-schema.org/draft/2020-12/schema",
"enum": [ "red", 123, true, { "foo": "bar" }, [ 1, 2 ], null ]
}
Valid
A boolean value that equals a value in the enumeration is valid
Instance
true
Valid
An object value that equals a value in the enumeration is valid
Instance
{ "foo": "bar" }
Invalid
An object value that does not equal a value in the enumeration is invalid
Instance
{ "foo": "baz" }