Observables Usage

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An interface can declare an observable object. This observable will notify observers (callback functions) when a certain event occurs.

Usage

This interface declares the observable "ObservablePing" that will notify observers when the function "Ping" is called:

Such a callback function must have the same return value and argument list as defined in the observable declaration:

// This example shows a function that can be used as an observer.
static maxon::Result<void> WatchPing(maxon::Int count)
{
DiagnosticOutput("Count: @", count);
return maxon::OK;
}
maxon::Int
Int64 Int
signed 32/64 bit int, size depends on the platform
Definition: apibase.h:196
DiagnosticOutput
#define DiagnosticOutput(formatString,...)
Definition: debugdiagnostics.h:170
maxon::OK
static const ERROR_OK OK
Definition: resultbase.h:40

The observable is accessible by the function of its name. An observer is added with maxon::ObservableBaseInterface::AddObserver():

// This example adds an observer to the "ObservablePing" observable.
g_observeMe.ObservablePing(true).AddObserver(WatchPing) iferr_return;
iferr_return
#define iferr_return
Definition: resultbase.h:1771

It is also possible to add lambdas to the observable.

// This example adds a lambda to the "ObservablePing" observable.
g_observeMe.ObservablePing(true).AddObserver(
[](maxon::Int count)
{
DiagnosticOutput("Count: @", count);
return maxon::OK;
}) iferr_return;

The observer functions are called when the specific event is triggered.

// This example calls the Ping() function which will notify all registered observers.
g_observeMe.Ping();

Further Reading