Adds Timer tracking funcitonality to NSObject

NSObject+SMATimer.m

#import <objc/runtime.h>

#import "SMAGlobal.h"
#import "CocoaLumberjack.h"

#import "NSObject+SMATimer.h"

#import "SMAMacros.h"
#import "SMABlockMacros.h"

static void *smaStartTimeKey = "smaTimerKey";

@implementation NSObject (SMATimer)

#pragma mark -
#pragma mark Public Methods

- (void)startTimer {
    objc_setAssociatedObject(self, smaStartTimeKey, [NSDate date], OBJC_ASSOCIATION_RETAIN);
}

- (void)stopTimerWithBlock:(void (^)(NSDate *startTime))block {
    SMABlockPerform(block, objc_getAssociatedObject(self, smaStartTimeKey));
    
    objc_setAssociatedObject(self, smaStartTimeKey, nil, OBJC_ASSOCIATION_RETAIN);
}

- (NSTimeInterval)stoppedTimeIntervalSinceStart {
    __block NSTimeInterval interval = 0;
    
    dispatch_semaphore_t sem = dispatch_semaphore_create(0);
    
    [self stopTimerWithBlock:^(NSDate *start) {
        interval = -[start timeIntervalSinceNow];
        
        dispatch_semaphore_signal(sem);
    }];
    
    dispatch_semaphore_wait(sem, DISPATCH_TIME_FOREVER);
    
    return interval;
}

- (void)stopLoadingInfoTimer {
    SMALogInfo(@"%@ loading time interval %f sec",
               [[self class] description],
               [self stoppedTimeIntervalSinceStart]);
}

@end