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<?php
declare(strict_types=1);
namespace OpenTelemetry\API\Metrics;
/**
* An observed callback.
*
* Callbacks that are bound to an object are automatically detached when the
* `ObservableCallbackInterface` and the bound object are out of scope.
* This means that the `ObservableCallbackInterface` can be ignored if the
* observed callback should be bound to the lifetime of the object.
* ```php
* class Example {
* function __construct(MeterProviderInterface $meterProvider) {
* $meterProvider->getMeter('example')
* ->createObservableGauge('random')
* ->observe(fn(ObserverInterface $observer)
* => $observer->observe(rand(0, 10)));
* }
* }
* ```
* Keeping a reference to the `ObservableCallbackInterface` within the bound
* object to gain a more fine-grained control over the life-time of the callback
* does not prevent garbage collection (but might require cycle collection).
*
* Unbound (static) callbacks must be detached manually using
* {@link ObservableCallbackInterface::detach()}.
* ```php
* class Example {
* private ObservableCallbackInterface $gauge;
* function __construct(MeterProviderInterface $meterProvider) {
* $this->gauge = $meterProvider->getMeter('example')
* ->createObservableGauge('random')
* ->observe(static fn(ObserverInterface $observer)
* => $observer->observe(rand(0, 10)));
* }
* function __destruct() {
* $this->gauge->detach();
* }
* }
* ```
*
* @see ObservableCounterInterface::observe()
* @see ObservableGaugeInterface::observe()
* @see ObservableUpDownCounterInterface::observe()
*/
interface ObservableCallbackInterface
{
/**
* Detaches the associated callback from the instrument.
*/
public function detach(): void;
}
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