RAC_Timestamp.m

RAC(self, timestamp) = [[RACObserve(self, model.timestamp) map:^id(NSDate *value) {
            return [[RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
                NSUInteger days, hours, minutes, seconds;
                absoluteTimeUnitsSinceDate(value, &days, &hours, &minutes, &seconds);
                NSUInteger updateAfter = NSNotFound;
                NSString *currentValue = nil;
                if (days) {
                    currentValue = [NSString stringWithFormat:@"%ud", (unsigned int)days];
                }
                else if (hours) {
                    currentValue = [NSString stringWithFormat:@"%uh", (unsigned int)hours];
                }
                else if (minutes) {
                    currentValue = [NSString stringWithFormat:@"%um", (unsigned int)minutes];
                    updateAfter = 60;
                }
                else {
                    if (seconds < 5.0) {
                        currentValue = @"just now";
                    }
                    else {
                        currentValue = [NSString stringWithFormat:@"%us", (unsigned int)seconds];
                    }
                    updateAfter = 1;
                }

                [subscriber sendNext:currentValue];
                RACSerialDisposable *disposable = [RACSerialDisposable serialDisposableWithDisposable:nil];
                if (updateAfter != NSNotFound) {
                    disposable.disposable = [[RACScheduler currentScheduler] afterDelay:updateAfter schedule:^{
                        [subscriber sendCompleted];
                    }];
                }
                return disposable;
            }] repeat];

        }] switchToLatest];