Operations on Object

The Object interface has a number of operations. We cannot define type Object in Slice because Object is a keyword; regardless, here is what the definition of Object would look like if it were legal:

sequence<string> StringSeq;

interface Object // "Pseudo" Slice!
{
    idempotent void ice_ping();
    idempotent bool ice_isA(string typeId);
    idempotent string ice_id();
    idempotent StringSeq ice_ids();
}

Note that, apart from the illegal use of the keyword Object as the interface name, the four operations are standard Slice operations and are mapped using the standard mapping rules.

ice_ping

All Ice objects support the ice_ping operation. That operation is useful for debugging because it provides a basic reachability test for an object: if the object exists and a message can successfully be dispatched to the object, ice_ping simply returns without error. If the object cannot be reached or does not exist, the ice_ping invocation throws a runtime exception that provides the reason for the failure.

ice_isA

The ice_isA operation accepts a type ID (such as the string returned by ice_id) and tests whether the target object implements this Slice interface returning true if it does. You can use this operation to check whether a target object implements a particular interface. For example, referring to the diagram Implicit Inheritance from Object once more, assume that you are holding a proxy to a target object of type AlarmClock. The table below illustrates the result of calling ice_isA on that proxy with various arguments. (We assume that all types in the Implicit inheritance from Object diagram are defined in a module Times):

Callingice_isAon a proxy denoting an object of type AlarmClock.

As expected, ice_isA returns true for ::Times::Clock and ::Times::AlarmClock and also returns true for ::Ice::Object. Obviously, an AlarmClock supports neither the Radio nor the RadioClock interfaces, so ice_isA returns false for these types.

ice_id

The ice_id operation returns the type ID of the most-derived Slice interface implemented by the target object.

ice_ids

The ice_ids operation returns a sequence of type IDs that contains the type IDs of all Slice interfaces implemented by the target object, in alphabetical order.

See Also

• Type IDs
• Interface Inheritance