On Jan 26, 2012, at 4:12 AM, Arved von Brasch wrote:
> - (NSString *)usedSpace {
> NSDictionary *systemInfo = [[NSFileManager defaultManager]
> attributesOfFileSystemForPath: [[NSBundle mainBundle] bundlePath] error: nil];
> NSDecimalNumber *total = [NSDecimalNumber decimalNumberWithString:
> [[systemInfo objectForKey: NSFileSystemSize] stringValue]];
> NSDecimalNumber *avail = [NSDecimalNumber decimalNumberWithString:
> [[systemInfo objectForKey: NSFileSystemFreeSize] stringValue]];
> return [self humanReadableNumber: [total decimalNumberBySubtracting:
> avail]];
> }
First, why are you using strings to convert to NSDecimalNumber? Ask the
NSNumber for its decimalValue and then use +[NSDecimalNumber
decimalNumberWithDecimal:]. That avoids formatting and parsing of strings.
Second, why do you need NSDecimalNumber? Can you not use either unsigned long
long or double for this purpose?
> This problem seems to depend on the compilation order. Commenting out the
> offending code, recompiling, then restoring the code and recompiling makes
> the problem go away. Performing a Clean operation than recompiling makes the
> problem reappear. This suggests compilation order affects whether the
> systemInfo dictionary has valid elements or not at runtime.
I doubt that. Probably, you have an uninitialized variable or stack smashing
bug somewhere and the compilation order affects the layout of the stack which
changes either what garbage is in the uninitialized variable or what on the
stack gets smashed.
Certainly, you can log the values you get from systemInfo to check your
hypothesis.
> As to why @dynamic is there, I thought that was the proper way to implement a
> property where the implementation was supplied by me rather than synthesised.
> Is that not the case?
You don't need @dynamic for properties where you supply the accessors at
compilation time. It's only necessary for when the accessors aren't apparently
available but will be at runtime. For example, by dynamically loading a
category or self-modifying code. (NSManagedObject uses something like the
latter.)
Regards,
Ken
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