How to get Nested JSON values [duplicate]

Question

EDIT:

Object result = JSON.deserializeUntyped(payload);

if (result instanceof Map<String, Object>) {
    Map<String, Object> resultMap = (Map<String, Object>)result;
    system.debug('result: ' + resultMap.get('records')); //returns null
}

//END EDIT

How to loop through the nested json key/value for an example how can I get the values for this attributes Records==>attributes==>url or Metadata=>formula

APEX Code:

String payload = '.... json...'
Map<String, Object> jsonMap = (Map<String, Object>)JSON.deserializeUntyped(payload);     

List<Object> records = (List<Object>) jsonMap.get('records'); //get the records
if (records != null) {
    for (Object r : records) {
        //for (string r2 : r.get('url')) {  //error incorrect signature
             system.debug(r.value);
        //}
    }
} else {
    system.debug('null.. : ' + records);
}

JSON

{
  "size": 1,
  "totalSize": 1,
  "done": true,
  "queryLocator": null,
  "entityTypeName": "CustomField",
  "records": [
    {
      "attributes": {
        "type": "CustomField",
        "url": "/services/data/v46.0/tooling/sobjects/CustomField/00N6g00000TAlZNEA1"
      },
      "Metadata": {
        "businessOwnerGroup": null,
        "businessOwnerUser": null,
        "formula": "IMAGE( \nCASE(Rating__c, \n\"Very Bad\", \"/img/samples/stars_100.gif\",\n\"Bad\", \"/img/samples/stars_200.gif\",\n\"Okay\", \"/img/samples/stars_300.gif\", \n\"Good\", \"/img/samples/stars_400.gif\", \n\"Very Good\", \"/img/samples/stars_500.gif\", \n\"/img/samples/stars_000.gif\"), \n\"rating\")",
        "formulaTreatBlanksAs": "BlankAsZero"
      }
    }
  ]
}

Answer 1

Below is how you deserialize in apex:

    String payload = '--payload--';
    Map<String, Object> jsonMap = (Map<String, Object>)JSON.deserializeUntyped(payload);     
    
    List<Object> records = (List<Object>) jsonMap.get('records'); //get the records
    if (records != null) {
        for (Object r : records) {
            Map<String,Object> rMap = (Map<String,Object>)r;
            Map<String,Object> attributes = (Map<String,Object>)rMap.get('attributes');
            Map<String,Object> Metadata = (Map<String,Object>)rMap.get('Metadata');
            System.debug(attributes);
        }
    } else {
        system.debug('null.. : ' + records);
    }

Note that there are invalid characters in formula in Metadata, so it will throw error, better to remove it and test. Later try to escape the new characters \n and check.

---

Better Solution

Whenever you are working in lightning components(aura or LWC), it is more efficient to return the string back to component to parse in javascript. Parsing in JS is much better and efficient than parsing in apex.

So, for the json you have given, below is how you can deserialize:

export default class App extends LightningElement {
    json = {
        "size": 1,
        "totalSize": 1,
        "done": true,
        "queryLocator": null,
        "entityTypeName": "CustomField",
        "records": [
            {
                "attributes": {
                    "type": "CustomField",
                    "url": "/services/data/v46.0/tooling/sobjects/CustomField/00N6g00000TAlZNEA1"
                },
                "Metadata": {
                    "businessOwnerGroup": null,
                    "businessOwnerUser": null,
                    "formula": "IMAGE( \nCASE(Rating__c, \n\"Very Bad\", \"/img/samples/stars_100.gif\",\n\"Bad\", \"/img/samples/stars_200.gif\",\n\"Okay\", \"/img/samples/stars_300.gif\", \n\"Good\", \"/img/samples/stars_400.gif\", \n\"Very Good\", \"/img/samples/stars_500.gif\", \n\"/img/samples/stars_000.gif\"), \n\"rating\")",
                    "formulaTreatBlanksAs": "BlankAsZero"
                }
            }
        ]
    };

    connectedCallback() {
        console.log(this.json.records);
        this.json.records.forEach(recItem=>{
            console.log(recItem.attributes.url);
            console.log(recItem.attributes.type);
        });
    }
}

Note that, you will be returning String from apex so you should parse it using JSON.parse.

Here is the working example