02-02-2010, 05:14 PM

I am really a .NET developer with some knowledge of x-code and objective C. What I am doing is calling a .NET web service to get a collection of Songs. I get these songs from the .NET web service: Name (String), Duration(TimeSpan), Hours(Int), Minutes(Int), and Seconds(Int). I only added the Hours, Minutes, and Seconds because I could not find any data type in objective C that would mimic the TimeSpan.

Now what I have to do is as they select multiple songs I need to add the Time of each song for a total duration of songs added.

Currently in the Music.h file I am using an NSDateComponent to hold the Hours, Minutes, and Seconds. Now I assume I could pull each piece out and add them up, make the conversion to handle seconds running over a minute, and stuff the total into another NSDateComponent, but there has to be an easier way.

Please help me find that easier way.
Thanks

02-02-2010, 06:18 PM

I'm not .NET developer (nor even a C# one), but I just read a quick summary of the TimeSpan type, and from my knowledge (and as you found) there is no comparable Cocoa type. With that in mind, I'd say your best bet will be to work with NSTimeIntervals behind the scenes, which are simply doubles that represent a number of seconds. From the TimeSpan summary I read, it looks like there's a TotalSeconds method, so perhaps you could just send that from the Web service and then work with it in your app as an NSTimeInterval.

Then when you're done doing whatever calculations you need to do (or more precisely, when you're ready to display the interval in a more readable form) you can convert it to an NSDateComponents object and use that for display. For example, if you have an array of the selected songs with a -combinedDuration method that returns an NSTimeInterval of the sum of all the songs' durations:

// Get the total duration of the songs.
NSTimeInterval totalDuration = [selectedSongs combinedDuration];

// Create two dates that are totalDuration apart for use
// in creating an NSDateComponents object.
NSDate *date1 = [NSDate date]; // Now.
NSDate *date2 = [NSDate dateWithTimeInterval:totalDuration 
                                   sinceDate:date1];

// Get the system calendar. If you're positive it will be the 
// Gregorian, you could use the specific method for that.
NSCalendar *currentCalendar = [NSCalendar currentCalendar];

// Specify which date components to get. This will get the hours, 
// minutes, and seconds, but you could do days, months, and so on
// (as I believe iTunes does).
NSUInteger unitFlags = NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit;

// Create an NSDateComponents object from these dates using the system calendar.
NSDateComponents *durationComponents = [currentCalendar components:unitFlags 
                                                          fromDate:date1 
                                                            toDate:date2 
                                                           options:0];

// Format this as desired for display to the user.
NSString *durationString = [NSString stringWithFormat:
      @"%d Hours, %d Minutes, and %d Seconds", 
      [durationComponents hour],
      [durationComponents minute], 
      [durationComponents second]];

// Display it however necessary. For example,
NSLog(@"The total duration of the selected songs is %@.", durationString);

Using this code, if I replace the first line with NSTimeInterval totalDuration = 5843;, I get this output:

The total duration of the selected songs is 1 Hours, 37 Minutes, and 23 Seconds.

Of course, you'd want to add some smarts as to whether to pluralize the time units (that is, whether to use "hour" or "hours"), and so on, but this should get you on the right track. Also, it should be significantly easier to work with NSTimeIntervals than NSDateComponents objects.

With assistance from the NSDate and NSDateComponents class references, the Date and Time Programming Guide for Cocoa, and this stackoverflow post.

02-03-2010, 11:43 AM

Thank you very much for the help. I appreciate the time you put into helping me. I will implement this today.

Thanks again.