This page provides a brief introduction to the Slice interfaces comprising the IceStorm service. See the online Slice API Reference XREF for the Slice documentation.

On this page:

The TopicManager Interface

The TopicManager is a singleton object that acts as a factory and repository of Topic objects. Its interface and related types are shown below:

{zcode:slice}
module IceStorm {
dictionary<string, Topic*> TopicDict;

exception TopicExists {
    string name;
};

exception NoSuchTopic {
    string name;
};

interface TopicManager {
    Topic* create(string name) throws TopicExists;
    idempotent Topic* retrieve(string name) throws NoSuchTopic;
    idempotent TopicDict retrieveAll();
    idempotent Ice::SliceChecksumDict getSliceChecksums();
};
};
{zcode}

The create operation is used to create a new topic, which must have a unique name. The retrieve operation allows a client to obtain a proxy for an existing topic, and retrieveAll supplies a dictionary of all existing topics. The getSliceChecksums operation returns Slice checksums for the IceStorm definitions.

The Topic Interface

The Topic interface represents a topic and provides several administrative operations for configuring links and managing subscribers.

{zcode:slice}
module IceStorm {
struct LinkInfo {
    Topic* theTopic;
    string name;
    int cost;
};
sequence<LinkInfo> LinkInfoSeq;

dictionary<string, string> QoS;

exception LinkExists {
    string name;
};

exception NoSuchLink {
    string name;
};

exception AlreadySubscribed {};

exception BadQoS {
    string reason;
};

interface Topic {
    idempotent string getName();
    idempotent Object* getPublisher();
    idempotent Object* getNonReplicatedPublisher();
    Object* subscribeAndGetPublisher(QoS theQoS, Object* subscriber)
        throws AlreadySubscribed, BadQoS;
    idempotent void unsubscribe(Object* subscriber);
    idempotent void link(Topic* linkTo, int cost)
        throws LinkExists;
    idempotent void unlink(Topic* linkTo) throws NoSuchLink;
    idempotent LinkInfoSeq getLinkInfoSeq();
    void destroy();
};
};
{zcode}

The getName operation returns the name assigned to the topic, while the getPublisher and getNonReplicatedPublisher operations return proxies for the topic's publisher object.

The subscribeAndGetPublisher operation adds a subscriber's proxy to the topic; if another subscriber proxy already exists with the same object identity, the operation throws AlreadySubscribed. The operation returns a proxy for a subscriber-specific publisher object.

The unsubscribe operation removes the subscriber from the topic.

A link to another topic is created using the link operation; if a link already exists to the given topic, the LinkExists exception is raised. Links are destroyed using the unlink operation.

Finally, the destroy operation permanently destroys the topic.

See Also

• Slice Checksums
• Using an IceStorm Publisher Object
• Publishing to a Specific Subscriber
• Topic Federation