Everyday Transit Hourly Interval Signal with an initial value.

MPXTransitDashboardViewModel.m

#import "DateTools.h"
#import "RACEXTScope.h"
#import "ReactiveCocoa.h"

@interface MPXTransitDashboardViewModel ()

/// ...

@end

@implementation MPXTransitDashboardViewModel

- (instancetype)init {

    // ...
    [self bindSignals];

}

- (void)bindSignals {

  // ... 
  
  RACSignal hourlyIntervalRefreshSignal = [self hourlyIntervalRefreshSignal]; 
  
  // ... 

}

- (RACSignal *)hourlyIntervalRefreshSignal {

    NSDate *now = [NSDate date];
    NSString *initialEventDateString = [NSString stringWithFormat:@"%d-%d-%d %d:00:00", now.year, now.month, now.day, now.hour + 1];
    [self.dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
    NSDate *initialEventDate = [self.dateFormatter dateFromString:initialEventDateString];
    NSTimeInterval initialEventDelay = [now secondsEarlierThan:initialEventDate];

    DDLogDebug(@"%@ - Hourly Interval Signal.  Initial Event Date: %@ Seconds: %f", NSStringFromClass([self class]), initialEventDateString, initialEventDelay);

    // Signal sends an initial value
    RACSignal *bootstrapSignal = [[RACSignal return:[NSDate date]] setNameWithFormat:@"Hourly Boostrap Event Signal"];
    // Then sends another event when the first hour rolls over
    // DAVE: Initially, I hadd a [RACSignal Empty] -delay:xx] but it never worked.  I found it needed an initial event sent through before completion for the delay to take effect.  
    RACSignal *initialEventSignal = [[[RACSignal return:[NSDate date]] delay:initialEventDelay] setNameWithFormat:@"Hourly Initial Event Signal"];
    // Then rolls over every hour thereafter ... 
    RACSignal *intervalEventSignal = [[RACSignal
            interval:60 * 60 // Refresh Every Hour
         onScheduler:[RACScheduler schedulerWithPriority:RACSchedulerPriorityDefault]]
            setNameWithFormat:@"Transit Trips Interval Refresh Signal"];
    RACSignal *bootstrappedInitialEventSignal = [bootstrapSignal concat:initialEventSignal];
    RACSignal *intervalRefreshSignal = [bootstrappedInitialEventSignal concat:intervalEventSignal];

    return intervalRefreshSignal;

}