Conditional JSON schema based on dynamic property value - json

Question

I'm trying to validate a JSON file that contains several nested components of the same type. Each component has a class string property. I'm trying to apply different validation schemas from my definitions to each component based on the value of class. Furthermore, the values of class can be "button-open", "button-close", "icon-message", "icon-...", "container", etc and I would like to apply the same validation schema for all the "buttons-" another to "icons-" and another to the rest.
The code I provide is what I have tried. I have excluded icons- for the shake of simplicity. As you can see I tried to match with a regular expression whenever there is button in class. Then it should constraint the minimum value of children elements to 1.
{
"$schema": "http://json-schema.org/draft-07/schema#",
"type": "object",
"required": ["results"],
"properties": {
"results": {
"type": "array",
"minItems": 1,
"items": {
"type": "object",
"anyOf": [
{
"$ref": "#/definitions/genericComponent"
},
{
"$ref": "#/definitions/button"
}
]
}
}
},
"definitions": {
"genericComponent": {
"type": "object",
"$id": "#/definitions/genericComponent",
"required":[
"class",
"children"
],
"properties":{
"class": {
"type": "string",
"description": "predicted class of the element(img, icon..)"
},
"children":{
"type": "array",
"description": "this element can contain more of the same type",
"items":{
"type": "object",
"anyOf":[
{"$ref": "#/definitions/button"},
{"$ref": "#/definitions/genericComponent"}
]
}
}
}
},
"button": {
"$id": "#/definitions/button",
"allOf":[
{"$ref": "#/definitions/genericComponent"},
{"properties": {
"class":{
"type":"string",
"pattern": "(button)"
},
"children":{
"type": "array",
"description": "this element must contain one generic element",
"items":{
"type": "object",
"$ref": "#/definitions/genericComponent"
},
"minItems": 1,
"maxItems": 1
}
}}
]
}
}
}
I also tried to apply the property conditionally as:
{
"type": "object",
"required": ["results"],
"properties": {
"results": {
"type": "array",
"minItems": 1,
"items": {
"type": "object",
"$ref": "#/definitions/genericComponent"
}
}
},
"definitions": {
"genericComponent": {
"type": "object",
"$id": "#/definitions/genericComponent",
"required":[
"class",
"children"
],
"properties":{
"class":{
"type": "string"
},
"children":{
"type": "array",
"items": {
"type": "object",
"anyOf":[
{"$ref":"#/definitions/genericComponent"},
{"$ref":"#/definitions/button"}
]
}
}
},
"if": {
"properties": {"class": {"pattern": "^button-rect$"}}
},
"then": {
"properties": {
"children":{
"type": "array",
"items": {
"type": "object",
"$ref": "#/definitions/genericComponent"
},
"minItems": 1,
}
}
},
"else": {
"properties": {
"children":{
"type": "array",
"items": {
"type": "object",
"$ref": "#/definitions/genericComponent"
}
}
}
}
}
}
}
EDIT: this one sample that pass but it shouldn't as the number of children of one of the buttons is highier of 1.
{"results": [
{
"class": "box",
"children": [
{
"class": "icon",
"children": []
},
{
"class": "button-rect",
"children": [
{
"class": "label",
"children": []
}
]
},
{
"class": "button-round",
"children": [
{
"class": "label",
"children": []
},
{
"class": "label",
"children": []
}
]
}
]
}
]
}

Answer 1

Your approach of applying conditionally was close, but had a few errors.
The reference for #/definitions/button couldn't be resolved, so you might have seen an error.
The regex you used in your if condition was for button-rect while you asked for it to cover button-round in your example. You could of course change it to a non anchored ^button- which sounds like what you want.
Here's the schema.
{
"type": "object",
"required": [
"results"
],
"properties": {
"results": {
"type": "array",
"minItems": 1,
"items": {
"type": "object",
"$ref": "#/definitions/genericComponent"
}
}
},
"definitions": {
"genericComponent": {
"type": "object",
"$id": "#/definitions/genericComponent",
"required": [
"class",
"children"
],
"properties": {
"class": {
"type": "string"
},
"children": {
"type": "array",
"items": {
"type": "object",
"anyOf": [
{
"$ref": "#/definitions/genericComponent"
}
]
}
}
},
"allOf": [
{
"if": {
"properties": {
"class": {
"pattern": "^button-round$"
}
}
},
"then": {
"properties": {
"children": {
"maxItems": 1
}
}
}
}
]
}
}
}
The then schema is applied to the instance. You don't need to repeat the constraints already expressed by the other part of that schema (with the $id of #/definitions/genericComponent). And by extension, you don't need the else either. (This isn't the same as writing code with an execution flow.)
You can see this schema in action against your JSON instance data at https://jsonschema.dev (link is preloaded with your schema and data)
Let me know if you have any questions. There are a number of issues with the first approach, but given this is the better approach, I'm not sure "fixing" the first one is in scope of this question. =]