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Closing long-lived resources in Kotlin – Glade Diviney – Medium

 6 years ago
source link: https://medium.com/@gladed/closing-long-lived-resources-in-kotlin-4e0b8e6ffbb7
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Closing long-lived resources in Kotlin

In this post I’ll show some of the problems with managing long-lived resources, and propose a simple utility class to help you solve them.

Quick, how many bugs can you spot in the following code:

  • What happens if someone calls start() or stop() twice?
  • What happens if close() throws?
  • Can resource be garbage collected after MyClass is stopped?
  • Is MyClass thread-safe with respect to resource?
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Some things are just hard to close safely.

Let’s address these issues:

Yuck. This works, but it’s a lot of boilerplate, exception-catching noise, a dangerous-looking var, potential synchronization issues, and ugly null objects.

We can do better with a utility class I call Closer (defined below). But first, let’s see it in action in a real-world(-ish) Android use case. Here, we create and initialize a MulticastLock, but only if it doesn’t already exist. And later we call its release() method, but only if it’s still hanging around:

Closer.kt

Here’s an implementation of Closer for use in your own projects.

AutoCloser is also included for wrapping AutoCloseable types.


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