Debug iPhone memory
I am using tools to try and determine if there are places in my application that might be more memory efficient. I took the time to mess around with the tools a bit, but I'm generally a newbie with hunting memory management issues coming from a Java background. I seem to be using about 1.82mb across calls to this method:
+ (NSString *)stringFromDateWithFormat:(NSDate *)date withFormat:(NSString *)format
{
NSDateFormatter *dateFormatter;
NSString *result;
if (nil == date || nil == format)
return nil;
result = nil;
if (nil != (dateFormatter = [[NSDateFormatter allocWithZone:[self zone]] init])) {
[dateFormatter setDateFormat:format];
if (nil != (result = [dateFormatter stringFromDate:date])) {
[dateFormatter release];
return result;
}
[dateFormatter release];
}
return nil;
}
Since I am releasing the date format I am wondering if the NSString result is my problem. It seems to me that the call to the stringFromDate library will return an auto-implementable object, so there is nothing I can do to manually manipulate it. Slightly unsure how to optimize this method.
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Is this method called many times in a loop? Autorelease objects are released only when the NSAutoreleasePool is released. As I understand it, a default autostart pool is created and released every event loop. You may be creating too many auto-implemented objects in a single event loop. The solution is to create a custom NSAutoreleasePool in the appropriate location and release it to clean up the autoreleasePool. An extreme example to illustrate the point:
int i;
NSAutoreasePool* pool = nil;
for (i = 0; i < 1000000; ++i) {
/* Create a new pool every 10000 iterations */
if ((i % 10000) == 0) {
if (pool) [pool release];
pool = [[NSAutoreleasePool alloc] init];
}
[someObj someMethodThatCreatesAutoreleasedObjects];
}
[pool release];
In this example, the current pool is released every 10,000 iterations and a new one is created. You can read more about memory management in the Programming Guide for Memory Management in Autodetect Pools.
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You need to return an auto-implemented object anyway, so you really have nothing to do with the resulting string. I don't see any memory related errors, but your code is definitely more verbose than necessary. Keep in mind that in Objective-C, if you call a method on nil, you return zero (or 0 for an integer, but not for floating point values). You can take out all those if statements and two return paths and your code will work the same. Also, I would just use alloc instead of allocWithZone.
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I'm not 100% with this. I am also just learning Mac / Iphone development. But you can use an auto-release pool to help with memory management. It is used to troubleshoot release issues.
Here is an article with lots on memory management . Check the left one-way menu.
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