Changes API: How to Subscribe to Counter Changes

C#Java

Subscribe to counter changes using ForCounter, ForCounterOfDocument, ForCountersOfDocument, or ForAllCounters.

The Subscribe method on the observable these methods return accepts only an IObserver object by default.
To instead subscribe with a delegate, like the change => ... lambda used in the examples below, add the System.Reactive package to your project.
This adds Subscribe overloads that take delegates, including ones with error and completion handlers.

• In this article:
  • ForCounter
  • ForCounterOfDocument
  • ForCountersOfDocument
  • ForAllCounters
  • CounterChange and CounterChangeTypes syntax

ForCounter

Counter changes can be observed using ForCounter method. This will subscribe changes from all counters with a given name, no matter in what document counter was changed.

Syntax

IChangesObservable<CounterChange> ForCounter(string counterName);

Parameters
counterName	string	Name of a counter to subscribe to.

Return Value
IChangesObservable<CounterChange>	Observable that allows to add subscriptions to counter notifications.

Example

IDisposable subscription = store
    .Changes()
    .ForCounter("Likes")
    .Subscribe(
        change =>
        {
            switch (change.Type)
            {
                case CounterChangeTypes.Increment:
                    // do something
                    break;
            }
        });

ForCounterOfDocument

Specific counter changes of a given document can be observed using ForCounterOfDocument method.

Syntax

IChangesObservable<CounterChange> ForCounterOfDocument(string documentId, string counterName);

Parameters
documentId	string	ID of a document to subscribe to.
counterName	string	Name of a counter to subscribe to.

Return Value
IChangesObservable<CounterChange>	Observable that allows to add subscriptions to counter notifications.

Example

IDisposable subscription = store
    .Changes()
    .ForCounterOfDocument("companies/1-A", "Likes")
    .Subscribe(
        change =>
        {
            switch (change.Type)
            {
                case CounterChangeTypes.Increment:
                    // do something
                    break;
            }
        });

ForCountersOfDocument

Counter changes of a specified document can be observed using ForCountersOfDocument method.

Syntax

IChangesObservable<CounterChange> ForCountersOfDocument(string documentId);

Parameters
documentId	string	ID of a document to subscribe to.

Return Value
IChangesObservable<CounterChange>	Observable that allows to add subscriptions to counter notifications.

Example

IDisposable subscription = store
    .Changes()
    .ForCountersOfDocument("companies/1-A")
    .Subscribe(
        change =>
        {
            switch (change.Type)
            {
                case CounterChangeTypes.Increment:
                    // do something
                    break;
            }
        });

ForAllCounters

Changes for all counters can be observed using ForAllCounters method.

Syntax

IChangesObservable<CounterChange> ForAllCounters();

Return Value
IChangesObservable<CounterChange>	Observable that allows to add subscriptions to counter notifications.

Example

IDisposable subscription = store
    .Changes()
    .ForAllCounters()
    .Subscribe(
        change =>
        {
            switch (change.Type)
            {
                case CounterChangeTypes.Increment:
                    // do something
                    break;
            }
        });

CounterChange and CounterChangeTypes syntax

• CounterChange
• CounterChangeTypes

The notification object delivered to subscribers when a counter changes.

class CounterChange
{
    CounterChangeTypes Type
    string Name
    long Value
    string DocumentId
    string CollectionName
    string ChangeVector
}

Property	Type	Description
Type	CounterChangeTypes	Counter change type enum
Name	string	Counter name
Value	long	Counter value after the change
DocumentId	string	Counter document identifier
CollectionName	string	Document's collection name
ChangeVector	string	Counter's ChangeVector

enum CounterChangeTypes
{
    None,
    Put,
    Delete,
    Increment,
}

Name	Value
None	0
Put	1
Delete	2
Increment	4