Retrieving the type by using `typeof`

Use the typeof operator to retrieve the run-time type of a data item.

The syntax of the typeof expression is shown below.

typeof expression

The example below demonstrates the syntax. The sample typeof expression evaluates to true.

var myVar : Integer = 10
if (typeof myVar == Integer) print("true")   // typeof myVar == Integer

Comparing the retrieved type to a subtype of the retrieved type evaluates to false. For example, the Integer type is a subclass of the Number class, which itself is a subclass of the Object class. All of the typeof expressions shown below evaluate to false.

if (typeof myVar == Number) print("false")   // typeof myVar != Number
if (typeof myVar == Object) print("false")   // typeof myVar != Object

The type of an entity or typekey is a parameterized type of Type<t>.

The following example shows some Type<t> types of a Producer entity and a NoteSecurityType typekey. The typeof expressions shown below evaluate to true.

if (typeof Producer == Type<Producer>) print("true")
if (typeof Producer == Type<entity.Producer>) print("true")
if (typeof NoteSecurityType == Type<NoteSecurityType>) print("true")
if (typeof NoteSecurityType == Type<typekey.NoteSecurityType>) print("true")

The Type<t> syntax must be used in comparison expressions of entities or typekeys that use the typeof operator. The expressions shown below evaluate to false because they do not use the required Type<t> syntax.

if (typeof Producer == Producer) print("false")
if (typeof Producer == entity.Producer) print("false")
if (typeof NoteSecurityType == NoteSecurityType) print("false")
if (typeof NoteSecurityType == typekey.NoteSecurityType) print("false")

The example below demonstrates how the run-time type retrieved by the typeof operator can differ from the type specified when the variable was defined.

var myVar : Object = 10
print(typeof myVar)         // Run-time type is java.lang.Integer

The run-time type of a null value is the void type as demonstrated below.

var myVar : Boolean = null
print(typeof myVar)         // Run-time type of the null value is void

Retrieving the type by using typeof

Retrieving the type by using `typeof`