I've run into a strange problem with a memory leak, apparently associated with
setting the text of UILabels. Googling for /UILabel memory leak/ shows several
other people having come up against similar problems, both with and without
ARC, but no solution.
My app (built with ARC) uses a timer to update a display of various components
of the time once a second. In Instruments, the Allocations tool reports a slow
but steady increase in persistent memory allocations of a single size, although
Leaks reports nothing. I've tried the iPad2 and iPhone6 simulators, both with
iOS 8.4. Both show this leakage, although at different rates and with
allocations of different sizes.
There are three UILabels that the app updates on every timer event. Commenting
out the three lines of code that look like this:
[[self someUILabel] setText: resultOfADateFormatter];
where someUILabel is the name of one of the three UILabel properties, removes
the leak. (All of the code that gets the date and formats it in three
different ways is still enabled.) Enabling any one of those three lines brings
the leak back. In the background, the app does not update the labels or
receive timer events, and does not leak.
The labels are declared as properties of my single view controller (by code
automatically generated by Xcode when I set up the storyboard) as:
@property (weak, nonatomic) IBOutlet UILabel *timestring;
@property (weak, nonatomic) IBOutlet UILabel *daystring;
@property (weak, nonatomic) IBOutlet UILabel *yearstring;
The rate of leakage is the same whether I am updating only one label on each
timer event or all three. If I reduce the timer interval from 1 second to 0.1
seconds, the rate of leakage increases by a factor of about 6. Definitely less
than 10.
The analyzer reports nothing, and building and validating an archive reports
nothing.
Is this a problem I can fix? Or is it a bug in Instruments, in the simulators,
or in iOS?
-- Richard Kennaway
--
Richard Kennaway, [email protected], http://www.cmp.uea.ac.uk/~jrk/
School of Computing Sciences,
University of East Anglia, Norwich NR4 7TJ, U.K.
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