Services

The Blue Alliance makes use of several service classes. Services are objects that encapsulate some amount of work and tend to be long-lived in memory. Services will generally respond to some external action and execute accordingly when necessary.

Retry Service - RetryService.swift

RetryService is a serviced used (exclusively) by other service classes to manage scheduling logic to be performed periodically. RetryService manages both the lifecycle and threading considerations for a Timer object. Only objects that conform to Retryable are able to be managed by a RetryService. RetryService should only be used within other services.

Retryable objects must must register with their RetryService via registerRetryable() to setup a timer and start receiving periodic calls to retry(). The duration between calls is set by retryInterval - the time internal in seconds, represented as a Double. RetryService can fire an initial execution of its Retryables retry() during registration by calling registerRetryable(initiallyRetry: true). This is useful for objects that execute a timed task in retry() to be executed immediately upon registering with their RetryService, as opposed to the next execution of their scheduled timer.

Keep in mind the lifecycle related to a Timer when using RetryService. A Timer created during registerRetryable() will hold a strong reference to it's Retryable object. Failing to call unregisterRetryable() when a Retryable is done with it's retry logic will keep the Retryable and RetryService objects in memory. Alternatively, if a service is meant to remain in memory for the lifespan of the app, avoid calling unregisterRetryable() if there are no other strong references to the object.

You can read more about Timer lifecycles from Apple's Using Timers documentation