forked from wezm/wezm.net
47 lines
2.1 KiB
HTML
47 lines
2.1 KiB
HTML
When it comes time to present errors or other messages in iOS
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with [UIAlertView] it becomes immediately obvious that a more
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convenient interface would involve the use of blocks. A [search on
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GitHub][github-search] shows just about every iOS developer has had a
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crack at it.
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[UIAlertView]: TODO
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[github-search]: https://github.com/search?type=Repositories&language=&q=uialertview&repo=&langOverride=&x=14&y=17&start_value=1
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After reviewing the better options (I.e. those that actually had a
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README with more than a few lines of content) on GitHub it appeared
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that one of the challenges was how to handle memory. This stems from
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the wrapper becoming the delegate for the UIAlertView but not having a
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strong reference from the caller. I saw various solutions to this, most
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involving adding a extra retain call to keep everything around until the
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delegate methods were called.
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Since my project is using ARC I looked for a solution that
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didn't involve marking the wrapper file as non-ARC and
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invoking `retain`. The solution I came up with was to use
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[`objc_setAssociatedObject`][set-object]. This Objective-C runtime
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function allows one object to be associated with another using various
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memory management strategies. I used this to associate the UIAlertView
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blocks based wrapper with the UIAlertView.
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[set-object]: http://developer.apple.com/library/ios/#documentation/Cocoa/Conceptual/ObjectiveC/Chapters/ocAssociativeReferences.html
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In the `init` method:
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objc_setAssociatedObject(alertView, _cmd, self, OBJC_ASSOCIATION_RETAIN);
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Note that I'm using the implicit second argument to the method, its
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selector, `_cmd` as the key for the associated object. This was
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suggested in a [tweet by Bill Bummager][bbum]. TODO
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[bbum]: http://twitter.com/bbum/status/3609098005
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Then in `alertView:didDismissWithButtonIndex:`, the association is
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removed, `dealloc` of the wrapper called and the `UIAlertView` also
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released.
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SEL key = @selector(initWithTitle:message:);
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objc_setAssociatedObject(self.alertView, key, nil, OBJC_ASSOCIATION_RETAIN);
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The full [MIT licensed code][gist] is available as a [gist on GitHub][gist].
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[gist]: https://gist.github.com/1392611
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