SORelativeDateTransformer is a value transformer that generates a human-readable phrase expressing the relative difference between a given date and the current date.
For example, when the current date-time is 2010-12-05 11:30, then
... 2010-12-04 11:00 is transformed to "30 minutes ago"
... 2010-12-01 11:00 is transformed to "5 days ago"
... 2010-12-25 08:00 is transformed to "in 2 weeks"
The transformer does not provide reverse transformations; you can only transform from an NSDate to an NSString.
Add the source files and strings bundle to your project.
SORelativeDateTransformer.h
SORelativeDateTransformer.m
SORelativeDataTransformer.strings
Instantiate an instance of SORelativeDateTransformer wherever you need to generate relative date phrases.
// Display a file's creation date relative to today's date
NSURL *someFilePath = ...;
NSDictionary *fileAttribs = [[NSFileManager defaultManager] attributesOfItemAtPath:someFilePath error:NULL];
NSDate *dateModified = [fileAttribs fileModificationDate];
// Date modified is 2010-10-01 12:00:00TZ; current date is 2010-10-30 12:00:00TZ
SORelativeDateTransformer *relativeDateTransformer = [[SORelativeDateTransformer alloc] init];
NSString *relativeDate = [relativeDateTransformer transformedValue: dateModified];
NSLog (@"This file was modified %@.", relativeDate); // ==> "This file was modified 3 weeks ago."
The accompanying SORelativeDateTransformer.strings file provides localizations for the date component names and their plural forms. Included are localization files for English, French, German, and Spanish.
The strings file also contains a localized string format template to use for relative past and future dates.
For past dates, the template for the English phrase is "%d %@ ago". For future dates, the template is "in %d %@".
Copy and modify the SORelativeDateTransformer.strings file with your own localizations.
Included is an iOS 4 interactive testing application. You can a date from the date picker and see the generated relative date string below.
SORelativeDateTransformer should be usable on iOS 3 and later, and Mac OS X 10.3 and later.
Use it, hack it, but give me some love.
SORelativeDateFormatter by William Garrison is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.
Based on a work at github.com.
Permissions beyond the scope of this license may be available at http://standardorbit.net.
