How do I introspect the class of a variable in APEX?

Question

I would like to know the class of a variable/property at runtime. For example:

Integer i = 5;

//pseudo-code
if (i.className == 'Integer') {
    System.debug('This is an integer.');
} else {
    System.debug('This is not an integer, but a ' + i.className);
}

I can't find the method/property that returns the class type in the documentation (assuming it's there). Am I missing it?

Answer 1

From p. 122 of the Apex Developer Guide:

If you need to verify at runtime whether an object is actually an instance of a particular class, use the instanceof keyword...

But, you cannot use the instanceof keyword on an instance of the the class of its subclasses or else you'll receive a compile error. For example:

Integer i = 0;
System.debug(i instanceof Integer);

>> COMPILE ERROR: Operation instanceof is always true since an instance of Integer is always an instance of Integer.

You need to use the instanceof keyword on superclasses only. For example:

System.debug((Object)i instanceof Integer);

>> true

If you ever need information on type of the Class itself, check the System.Type methods (pg 396 of current Apex developer's guide. Here's are some examples:

Type integerType;
integerType = Type.forName('Integer');
integerType = Integer.class;

Answer 2

Someone asked me this earlier today. Here is a more dynamic solution.

MyClass mine     = new MyClass();
String myStr     = String.valueOf(mine);
String className = myStr.split(':')[0];
System.assertEquals('MyClass', className);

Answer 3

A generic code of Salesforce Apex to explain :

public class Animal {}
public class Bird extends Animal {}

Animal a = new Bird();                      // Success
System.debug(a);                            // Bird:[]
System.debug((Bird)a);                      // Bird:[]
System.debug((Animal)a);                    // Bird:[]
System.debug(a instanceof Bird);            // true
System.debug((Animal)a instanceof Bird);    // true
System.debug((Bird)a instanceof Bird);      // Operation instanceof is always true since an instance of Bird is always an instance of Bird
System.debug((Bird)a instanceof Animal);    // Operation instanceof is always true since an instance of Bird is always an instance of Animal

Answer 4

Just to add more information regarding toString() and String.valueOf().

String.valueOf() can not be relied upon to get the name of a Apex class at runtime. I don't think this is documented but if you add an toString() method to your custom class with the override keyword, then String.valueOf() will use that to determine the string value of your object.

class MyClassDefaultToString {
}

class MyClassOverrideToString {
    public override String toString() {
        return 'override toString';
    }
}

MyClassDefaultToString c1 = new MyClassDefaultToString();
System.assertEquals('MyClassDefaultToString:[]', String.valueOf(c1));

MyClassOverrideToString c2 = new MyClassOverrideToString();
System.assertNotEquals('MyClassOverrideToString:[]', String.valueOf(c2));
System.assertEquals('override toString', String.valueOf(c2));

Answer 5

This works for me

Map<String, Object> m =  (Map<String, Object>)JSON.deserializeUntyped(JSON.serialize(myObjectInstance));
Map<String, Object> mComplexProperty = (Map<String, Object>)m.get('complexProperty');
String mSimpleProperty = (String)m.get('simpleProperty');

I'm not sure if the JSON serialization and deserialization will overhead, but... for now it's working

Answer 6

What if you need the FQCN instead of the class name (such as what you'd get from Java's getName())? Here is what you can do.

public class Beasts {
  public interface Animal {}
  public virtual class Bird implements Animal {}
  public class Robin extends Bird {}
}

System.assertEquals(
  Robin.class,
  Type.forName(ObjUtil.getName(new Robin(), true))
);
System.assertEquals(
  Robin.class,
  Type.forName(ObjUtil.getName((Animal)new Robin(), true)))
);
System.assertEquals(
  Robin.class,
  Type.forName(ObjUtil.getName((Bird)new Robin(), true)))
);

public class ObjUtil {
  public static String getName(Object obj, Boolean isQualifiedName) {
    // Qualified name
    if (isQualifiedName) {
      try {
        if (0 == (Long) obj) {
        }
      } catch (Exception ex) {
        typeName = ex.getMessage().remove('Invalid conversion from runtime type ').remove(' to Long');
        System.debug('typeName = ' + typeName);
        return typeName;
      }
    } else {
      // Class name
      typeName = String.valueOf(obj);
      if (typeName.indexOf(':[') != -1) {
        typeName = typeName.split(':')[0];
        System.debug('typeName = ' + typeName);
        return typeName;
      }
    }
  }
}

Answer 7

Not ideal, but here's a way to get this done:

public String getClassType(Object o)
{
    String retVal = 'Unknown';

    if(o instanceof Klass1)
        retVal = 'Klass1';
    else if(o instanceof Klass2)
        retVal = 'Klass2';
    else if(o instanceof Klass3)
        retVal = 'Klass3';

    return retVal;
}