## Use `IF..Then..Else` [new in Draft-07][1] 




<pre><code>{
 "$schema": "http://json-schema.org/draft-07/schema#",
 "type": "array",
 "items": {
 "type": "object",
 "properties": {
 "controlType": {
 "type": "string",
 "enum": ["title", "dropdown", "button"]
 },
 "options:": {
 "type": "array",
 "items": {"type": "string"}
 }
 },
 
 "if": {
 "properties": {
 "controlType": {"const": "dropdown"}
 }
 },
 "then": {
 "required": ["options"]
 }
 }
}
</code></pre>


## Use [`oneOf`][6] or [`anyOf`][5]

This can be useful if you have a property that has a limited number of acceptable values (such as an enum), but each possible value needs to be individually mapped. 




<pre><code>{
 "$schema": "http://json-schema.org/draft-07/schema#",
 "type": "array",
 "items": {
 "type": "object",
 "properties": {
 "controlType": {
 "type": "string",
 "enum": ["title", "dropdown", "button"]
 },
 "options:": {
 "type": "array",
 "items": {"type": "string"}
 }
 }, 
 "anyOf": [
 {
 "properties": {
 "controlType": {"const": "dropdown"}
 },
 "required": ["controlType", "options"]
 },
 {
 "properties": {
 "controlType": {"const": "title"}
 },
 "required": ["controlType"]
 },
 {
 "properties": {
 "controlType": {"const": "button"}
 },
 "required": ["controlType"]
 }
 ]
 }
}
</code></pre>


### Further Reading

* [Conditionally require attribute][2]
* [Applying subschemas conditionally][3]
* [Combining schemas][4]





[1]: http://json-schema.org/draft-07/json-schema-release-notes.html
[2]: https://stackoverflow.com/a/38781027/1366033
[3]: https://json-schema.org/understanding-json-schema/reference/conditionals.html
[4]: https://json-schema.org/understanding-json-schema/reference/combining.html
[5]: https://json-schema.org/understanding-json-schema/reference/combining.html#anyof
[6]: https://json-schema.org/understanding-json-schema/reference/combining.html#oneof

I'm building a json schema definition which has a fixed set of controls that I've currently limited with an `enum`. However, not all properties are relevant for all controls.  

I only want to require an `options` property if the `controlType` = `dropdown`

```js
{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "type": "array",
  "items": {
    "type": "object",
    "properties": {
      "controlType": {
        "type": "string",
        "enum": ["title", "dropdown", "button"]
      },
      "options:": {
        "type": "array",
        "items": {"type": "string"}
      }
    }
  }
}
```

How can I conditionally include / require a field in a json schema?