Question

Here’s a simple class:

#import "One.h"
#import "Two.h"

@implementation DataFileRegistrar

static NSMutableDictionary *elementToClassMapping;

+ (void)load
{
    [self registerClass:[One class] forElement:@"one"];
    [self registerClass:[Two class] forElement:@"two"];
}

+ (void)registerClass:(Class)class forElement:(NSString *)element
{
    if (!elementToClassMapping) {
        elementToClassMapping = [NSMutableDictionary dictionaryWithObject:class forKey:element];
    } else {
        [elementToClassMapping setValue:class forKey:element];
    }
}

+ (id)classForElement:(NSString *)element
{
    return [elementToClassMapping valueForKey:element];
}

@end

The problem is this compiler message:

objc[7172]: Object 0x6840720 of class __NSCFDictionary autoreleased with no pool in place - just leaking - break on objc_autoreleaseNoPool() to debug

Any ideas what’s going on?

Basically, I want to have a simple class with a couple of class methods and one static dictionary. It would be always used without instantiation. I want to use it for a couple of things right after the app starts and then I want to release its memory. I thought ARC can take care of this.

Answer 1

Your class’ +load is calling methods which calls autorelease.

Your class is loaded before main.

You can explicitly create an autorelease pool in +load:

+ (void)load
{
    @autoreleasepool {
        [self registerClass:[One class] forElement:@"one"];
        [self registerClass:[Two class] forElement:@"two"];
    }
}

However, it’s often better to guarantee the order of your program’s initialization and load explicitly before creating any threads in main:

int main(int argc, const char * argv[]) {
  @autoreleasepool {
      [DataFileRegistrar initializeStaticStuff];
      ...