Lifetime

The JetBrains.DataFlow.Lifetime class is used for cleanup code and resource management. Lifetime is similar to, but different from IDisposable. In fact, you can consider Lifetime to be the "dual" of IDisposable.

IDisposable is best suited to deterministic cleanup of a limited number of objects in a small scope. That is, it's ideal when you have created one or maybe two objects that need cleanup at a specific point in code; the using keyword makes this particularly easy.

However, when dealing with multiple objects that require cleanup, or that live longer than a single method call, more and more code is required for housekeeping of the IDisposable instances, including providing the means to invoke Dispose. This pattern can quickly and easily spread to calling code, meaning a lot of extra code is required just to manage resources and cleanup.

The Lifetime class reduces this boilerplate by approaching the issue from the opposite direction. It is responsible for the housekeeping of the clean up tasks. Calling code can register callbacks with the Lifetime, and when it's terminated, those callbacks are executed, in reverse order, performing any required cleanup. This way, the housekeeping is moved out of user code.

Instead of returning an IDisposable object that knows how to perform cleanup, and which needs collating and disposing, a method that needs to perform cleanup will accept a Lifetime instance, and register a callback that performs the cleanup. Now a single instance is maintaining all of the cleanup code, and there is no resource management housekeeping code in the calling class.

Furthermore, the Lifetime class allows for "nested" Lifetime instances, which can either be terminated independently, or when parent Lifetime terminates.