In computing, type introspection is a capability of some object-oriented programming languages to determine the type of an object at runtime. This is a notable capability of the Objective-C language, and is a common feature in any language that allows object classes to be manipulated as First-class objects by the programmer.

In Objective-C, for example, both the generic Object and NSObject (in Cocoa/OpenStep) provide the method isMemberOfClass: which returns true if the argument to the method is an instance of the specified class. The method isKindOfClass: analogously returns true if the argument inherits from the specified class.

For example, say we have a Puppy and Kitten class inheriting from Animal, and a Vet class.

Now, in the desex method we can write - desex: (id) to_desex { if(isKindOfClass:^*) { //we're actually desexing an Animal, so continue if(isMemberOfClass:^*) desex_dog(to_desex); else if(isMemberOfClass:^*) desex_cat(to_desex); else error(); } else { error(); } }

Now, when desex is called with a generic object (an id), the function will behave correctly depending on the type of the generic object.

Type introspection can be used to implement polymorphism.

See also

• Introspector (program)

Object-oriented programming