Don't pass the observer as the context: argument; pretty much anything
else is better. Passing NULL (just, for example) flattens the curve
quite a bit. If you have nothing better to pass in, put this in your
code and pass the address of it:
static char _xyzzy_ = 0;
Chris Kane
Cocoa Frameworks, Apple
On Aug 3, 2009, at 6:51 AM, Andreas Känner wrote:
Hi,
If you add more and more key/value observers with
addObserver:forKeyPath:options:context: this call takes longer and
longer in a non-linear way.
I posted a bug report today (ID: 7112953) but maybe someone already
has a workaround. Here is my sample code:
#include <Foundation/Foundation.h>
@interface ModelObject : NSObject
{
NSString* title;
}
@property (readwrite, copy) NSString* title;
@end
@implementation ModelObject
@synthesize title;
@end
@interface Observer : NSObject
{}
@end
@implementation Observer
@end
void addObservers(NSUInteger count)
{
// Create model objects and observers:
NSMutableArray* modelObjects = [NSMutableArray
arrayWithCapacity:count];
NSMutableArray* observers = [NSMutableArray
arrayWithCapacity:count];
for(NSUInteger i=0; i<count; i++)
{
[modelObjects addObject:[[ModelObject alloc] init]];
[observers addObject:[[Observer alloc] init]];
}
// Register observers:
NSDate* startDate = [NSDate date];
for(NSUInteger i=0; i<count; i++)
{
ModelObject* modelObject = [modelObjects objectAtIndex:i];
Observer* observer = [observers objectAtIndex:i];
[modelObject addObserver:observer
forKeyPath:@"title"
options:NSKeyValueObservingOptionNew |
NSKeyValueObservingOptionOld
context:observer];
}
NSLog(@"time to add %d observers: %f s", count, -[startDate
timeIntervalSinceNow]);
}
int main (int argc, const char * argv[])
{
NSAutoreleasePool* pool = [NSAutoreleasePool new];
addObservers(10);
addObservers(100);
addObservers(1000);
addObservers(10000);
[pool release];
}
In my test case an observer does always observe only one object and
each observed object is only observed by one observer. I think this
is a common use case.
I have results for Snow Leopard too, but I think I'm not allowed to
post them on this mailing list. Here are the results for Leopard:
I tested this with different build settings (with/without GC and
32/64bit)
Machine: iMac 2.4 GHz Intel Core 2 Duo
Leopard (10.5.7/9J61):
32Bit:
With GC:
time to add 10 observers: 0.001008 s
time to add 100 observers: 0.001796 s
time to add 1000 observers: 0.174864 s
time to add 10000 observers: 10.746330 s
Without GC:
time to add 10 observers: 0.000920 s
time to add 100 observers: 0.000956 s
time to add 1000 observers: 0.056894 s
time to add 10000 observers: 4.615175 s
64Bit:
With GC:
time to add 10 observers: 0.001340 s
time to add 100 observers: 0.001533 s
time to add 1000 observers: 0.125700 s
time to add 10000 observers: 7.545702 s
Without GC:
time to add 10 observers: 0.001058 s
time to add 100 observers: 0.000831 s
time to add 1000 observers: 0.053189 s
time to add 10000 observers: 4.006754 s
Notes:
If you know a workaround for this bottleneck please drop me an email.
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