Fix issues in ImageDownload and ImageDownloader #3072
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- Fix a lot of thread-safety issues.
- Fix incorrect handling of errors:
- Completions are called two times for HTTP status code >= 400.
- `ImageDownload` operation wasn't properly transition into finished
state.
- `ImageDownload` operation didn't have proper `isReady` state.
- Increase test coverage for these types.
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S2Ler
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Jun 11, 2021
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| // So we trigger `init` here so that `urlSession` is initialized in a thread safe manner. | ||
| _ = urlSession |
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Does the lazy syntax benefit us here? Maybe it’d be simpler to inline that initialization here.
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Good questions, thanks for asking. Without going deep into explaining the rationale why I've kept lazy var I think we can change private lazy var urlSession: URLSession to private var urlSession: URLSession!.
There is no need for dynamic dispatch. This class doesn't have subclasses and not intended to have.
Sorry, can you please rephrase? |
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Fixes #3067
ImageDownloadoperation wasn't properly transition into finishedstate.
ImageDownloadoperation didn't have properisReadystate.Implementation
ImageDownloaderImageDownloaderis fixed by properly using Dispatch Queue: perform protected state read/write inside the queue.accessQueuereplaced by a serial one, because most accesses to the queue modifies the protected state that require a barrier to be placed. That makes theaccessQueuemerely a serial queue.ImageDownloadImageDownloadis a subclass of NSOperation.Statevariable. No more multiple flags juggling.objc_sync_enterwith a lock.