Below i the code :

Map<String,Object> poVals = 

     system.debug('poVals' +poVals);
     lstPODetails = (List<object>)poVals.get('purchaseOrders'); 
     system.debug('lstPODetails' +lstPODetails);
     String poFormat = lstPODetails.get(0).FORMAT;

when trying to access a variable from 1st element of list in the last line, it says that variable doesn't exist : FORMAT What do you think is wrong here.


The Object type does not contain any attributes or methods by default. You need to cast it to a concrete type to access any properties on a particular instance. For instance, if you had a PurchaseOrderWrapper class defined as below, you would deserialize into a List<PurchaseOrderWrapper> instead of List<Object>.

public with sharing class PurchaseOrderWrapper
    final String format;

Instead of:

Map<String, Object> response = (Map<String, Object>)JSON.deserializeUntyped(payload);
List<Object> data = (List<Object>)response.get('purchaseOrders');


List<PurchaseOrderWrapper> data = 

You can read more about the Object type in the Apex Developer Guide under Primitive Data Types:

Any data type that is supported in Apex. Apex supports primitive data types (such as Integer), user-defined custom classes, the sObject generic type, or an sObject specific type (such as Account). All Apex data types inherit from Object.

You can cast an object that represents a more specific data type to its underlying data type. For example:

Object obj = 10;
// Cast the object to an integer.
Integer i = (Integer)obj;
System.assertEquals(10, i);

The next example shows how to cast an object to a user-defined type—a custom Apex class named MyApexClass that is predefined in your organization.

Object obj = new MyApexClass();
// Cast the object to the MyApexClass custom type.
MyApexClass mc = (MyApexClass)obj;
// Access a method on the user-defined class.

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