allOf : Array<Schema>
allOf
Array<Schema>An instance validates successfully against this keyword if it validates successfully against all schemas defined by this keyword’s value.
| Value | This keyword must be set to a non-empty array, where each item is a valid JSON Schema |
|---|---|
| Kind | Applicator |
| Applies To | Any |
| Base Dialect | 2020-12 |
| Changed In | None |
| Introduced In | Draft 4 |
| Vocabulary | Applicator |
| Specification | https://json-schema.org/draft/2020-12/json-schema-core.html#section-10.2.1.1 |
| Metaschema | https://json-schema.org/draft/2020-12/meta/applicator |
| Official Tests | draft2020-12/allOf.json |
| Default |
As if it was set to the (invalid) value:
[]
|
| Annotation | None |
| Affected By | None |
| Affects | None |
| Also See |
|
The allOf keyword restricts instances to validate against every given subschema. This keyword can be thought of as a logical conjunction (AND) operation, as instances are valid if they satisfy every constraint of every subschema (the intersection of the constraints).
Common Pitfall
Wrapping a single instance of the $ref
or $dynamicRef keyword in an allOf operator is an
anti-pattern.
This practice has historical roots. In JSON Schema Draft 7 and
earlier versions, any subschema declaring the $ref keyword was considered to
be a reference object and any other sibling keyword was silently ignored. As
a consequence, subschemas with references that made use of other keywords had
to artificially wrap the reference into its own subschema.
Best Practice
This keyword typically has a single use case: combining multiple schemas through the use of (internal or external) references. If this is not the case, prefer elevating the keywords of every subschema to the outer schema and avoid using this keyword.
This keyword is equivalent to the && operator found in most programming
languages. For example:
bool valid = A && B && C;
As a reference, the following boolean truth table considers the evaluation result of this keyword given 3 subschemas: A, B, and C.
allOf |
Subschema A | Subschema B | Subschema C |
|---|---|---|---|
| Invalid | Invalid | Invalid | Invalid |
| Invalid | Invalid | Invalid | Valid |
| Invalid | Invalid | Valid | Invalid |
| Invalid | Invalid | Valid | Valid |
| Invalid | Valid | Invalid | Invalid |
| Invalid | Valid | Invalid | Valid |
| Invalid | Valid | Valid | Invalid |
| Valid | Valid | Valid | Valid |
Examples
{
"$schema": "https://json-schema.org/draft/2020-12/schema",
"allOf": [
{ "$ref": "#/$defs/foo" },
{ "$ref": "#/$defs/bar" }
],
"$defs": {
"foo": { "type": "number" },
"bar": { "type": "integer" }
}
}123453.14"Hello World"