UIDocument and non-thread-safe Model
UIDocument and non-thread-safe Model
- Subject: UIDocument and non-thread-safe Model
- From: Manfred Schwind <email@hidden>
- Date: Sun, 27 May 2012 22:35:18 +0200
Hi,
when using UIDocument, reading and writing the document is done asynchronously in a separate thread. But there's one thing I don't understand: how is that supposed to be used with non-thread-safe models? In my opinion most straight-forward implemented models are _not_ thread-safe.
If you have the common case of a non-thread-safe model - is there an easy way to let UIDocument do reading/writing synchronously at the main thread? Or are we supposed to serialize every (!) modification of the model in a performAsynchronousFileAccessUsingBlock call?
Initially reading the document (triggered by openWithCompletionHandler) is usually not a problem. The user can not work with the model before it has been loaded. The problems begin when writing the document: the document write methods are called asynchronously, so the model is accessed at this time, but the user can do things at the same time in parallel through the UI and modify the model at the same time as it is saved - a big source for unpredicted behaviour, data-loss, crashes ...
The documentation for performAsynchronousFileAccessUsingBlock only mentions accessing the "document" (assuming this means the document's file?). But I think serializing the file access is not enough; accessing the "in-memory" model must also be serialized. Or did I miss something?
Regards,
Mani
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