Use the forName methods to retrieve the type of an Apex class, which can be a built-in or a user-defined class. You can use these methods to retrieve the type of public and global classes, and not private classes even if the context user has access. Also, use the newInstance method if you want to instantiate a Type that implements an interface and call its methods while letting someone else, such as a subscriber of your package, provide the methods’ implementations.
The following sample shows how to use the Type methods to instantiate a Type based on its name. A typical application of this scenario is when a package subscriber provides a custom implementation of an interface that is part of an installed package. The package can get the name of the class that implements the interface through a custom setting in the subscriber’s org. The package can then instantiate the type that corresponds to this class name and invoke the methods that the subscriber implemented.
In this sample, Vehicle represents the interface that the VehicleImpl class implements. The last class contains the code sample that invokes the methods implemented in VehicleImpl.
global class VehicleImpl implements Vehicle { global Long getMaxSpeed() { return 100; } global String getType() { return 'Sedan'; } }
public class CustomerImplInvocationClass { public static void invokeCustomImpl() { // Get the class name from a custom setting. // This class implements the Vehicle interface. CustomImplementation__c cs = CustomImplementation__c.getInstance('Vehicle'); // Get the Type corresponding to the class name Type t = Type.forName(cs.className__c); // Instantiate the type. // The type of the instantiated object // is the interface. Vehicle v = (Vehicle)t.newInstance(); // Call the methods that have a custom implementation System.debug('Max speed: ' + v.getMaxSpeed()); System.debug('Vehicle type: ' + v.getType()); } }
The class property returns the System.Type of the type it is called on. It is exposed on all Apex built-in types including primitive data types and collections, sObject types, and user-defined classes. This property can be used instead of forName methods.
System.Type t = Integer.class;
You can use this property for the second argument of JSON.deserialize, deserializeStrict, JSONParser.readValueAs, and readValueAsStrict methods to get the type of the object to deserialize. For example:
Decimal n = (Decimal)JSON.deserialize('100.1', Decimal.class);
The following are methods for Type.
public Boolean equals(Object typeToCompare)
Type: Boolean
Type t1 = Account.class; Type t2 = Type.forName('Account'); System.assert(t1.equals(t2));
public static System.Type forName(String fullyQualifiedName)
Type: System.Type
public static System.Type forName(String namespace, String name)
Type: System.Type
This example shows how to get the type that corresponds to the ClassName class and the MyNamespace namespace.
Type myType = Type.forName('MyNamespace', 'ClassName');
public String getName()
Type: String
This example shows how to get a Type’s name. It first obtains a Type by calling forName, then calls getName on the Type object.
Type t = Type.forName('MyClassName'); String typeName = t.getName(); System.assertEquals('MyClassName', typeName);
public Integer hashCode()
Type: Integer
The returned hash code value corresponds to the type name hash code that String.hashCode returns.
public Boolean isAssignableFrom(Type sourceType)
Type: Boolean
Unlike the instanceof operator, this method allows you to check type compatibility without having to create a class instance. This method eliminates static compile-time dependencies that instanceof requires.
//Scenario: Managed package code loading a “plugin” class that implements a managed interface; the implementation done outside of the package String pluginNameStr = Config__c.getInstance().PluginApexType__c; Type customerProvidedPluginType = Type.forName(pluginNameStr); Type pluginInterface = ManagedPluginInterface.class; // Constructors may have side-effects, including potentially unsafe DML/callouts. // We want to make sure the class is really designed to be a valid plugin before we instantiate it Boolean validPlugin = pluginInterface.isAssignableFrom(customerProvidedPluginType); // validate that it implements the right interface if(!validPlugin){ throw new SecurityException('Cannot create instance of '+customerProvidedPluginType+'. Does not implement ManagedPluginInterface'); }else{ return Type.newInstance(validPlugin); }
The following code snippet first defines sibling classes A and B that both implement the Callable interface and an unrelated class C. Then, it explores several type comparisons using isAssignableFrom().
//Define classes A, B, and C global class A implements Database.Batchable<String>, Callable { global Iterable<String> start(Database.BatchableContext context) { return null; } global void execute(Database.BatchableContext context, String[] scope) { } global void finish(Database.BatchableContext context) { } global Object call(String action, Map<String, Object> args) { return null; } } global class B implements Callable { global Object call(String action, Map<String, Object> args) { return null; } } global class C { }
Type listOfStrings = Type.forName('List<String>'); Type listOfIntegers = Type.forName('List<Integer>'); boolean flagListTypes = listOfIntegers.isAssignableFrom(listOfStrings); // false
//Examples with stringType and idType Type stringType = Type.forName('String'); Type idType = Type.forName('Id'); boolean isId_assignableFromString = idType.isAssignableFrom(stringType); // true //isAssignableFrom respects that String can be assigned to Id without an explicit cast
//Examples with typeA, typeB, and typeC Type typeA = Type.forName('A'); Type typeB = Type.forName('B'); Type typeC = Type.forName(’C’); boolean isTypeB_ofTypeA = typeB.isAssignableFrom( typeA ); // false - siblings boolean isTypeA_ofTypeC = typeA.isAssignableFrom( typeC ); // false - unrelated types boolean isTypeA_ofTypeA = typeA.isAssignableFrom(typeA); // true - identity
//Examples with callableType and batchableType Type callableType = Type.forName('Callable'); Type batchableType = Type.forName('Database.Batchable'); boolean isTypeA_Callable = callableType.isAssignableFrom( typeA ); // true - type A is a child of Callable type boolean isTypeA_Batchable = batchableType.isAssignableFrom( typeA ); // true - type A is a child of Batchable type boolean isCallableOfTypeA = typeA.isAssignableFrom( callableType ); // false - Callable type is not a child of type A boolean isBatchableOfTypeA = typeA.isAssignableFrom( batchableType ); // false - Batchable type is not a child of type A
public Object newInstance()
Type: Object
Because newInstance returns the generic object type, you should cast the return value to the type of the variable that will hold this value.
This method enables you to instantiate a Type that implements an interface and call its methods while letting someone else provide the methods’ implementation. For example, a package developer can provide an interface that a subscriber who installs the package can implement. The code in the package calls the subscriber's implementation of the interface methods by instantiating the subscriber’s Type.
This example shows how to create an instance of a Type. It first gets a Type by calling forName with the name of a class (ShapeImpl), then calls newInstance on this Type object. The newObj instance is declared with the interface type (Shape) that the ShapeImpl class implements. The return value of the newInstance method is cast to the Shape type.
Type t =
Type.forName('ShapeImpl');
Shape newObj =
(Shape)t.newInstance();
public String toString()
Type: String
This method returns the same value as getName. String.valueOf and System.debug use this method to convert their Type argument into a String.
This example calls toString on the Type corresponding to a list of Integers.
Type t = List<Integer>.class; String s = t.toString(); System.assertEquals('List<Integer>', s);