Apple Objective-C programming fundamentals. Working with Dates

When you need to display date and time on your app’s screen you need an easy way to convert NSDate objects to NSString objects. Objective-C  contains methods to do the conversion, but the syntax is not simple. It is much easier to create a method that does the conversion and call that in a central place.

Create a method to convert NSDate objects to NSString using the current date format of the device.

Add a new class to the project

• Click the + sign in the lower left corner of the Project Navigator
• Select New File… in the pop-up menu
• Select IOS -> Cocoa Touch -> Objective-C class
• Click the Next button
• Enter CommonMenthods into the Class field
• Select NSObject in the Subclass of list
• Click the Next button
• Click the Create button to save the file in the project folder

Add three method signatures to the CommonMethods class

• Open the CommonMethods.h file
• Insert the following code into the @interface section

  + (NSString *)getDateShortString:(NSDate *)date;
  + (NSString *)getTimeShortString:(NSDate *)date;
  + (NSString *)getDateAndTimeShortString:(NSDate *)date;
  
  

Add the three methods to the implementation file

• Open the CommonMethods.m file
• Insert the following code into the@implementation section of the file

  // Returns the short date as a string
  + (NSString *)getDateShortString:(NSDate *)date {
      
      NSString *stringFromDate = [NSDateFormatter localizedStringFromDate:date
                                                                dateStyle:NSDateFormatterShortStyle
                                                                timeStyle:NSDateFormatterNoStyle];
      
      return stringFromDate;
  }
  
  // Returns the short time as a string
  + (NSString *)getTimeShortString:(NSDate *)date {
      
      NSString *stringFromDate = [NSDateFormatter localizedStringFromDate:date
                                                                dateStyle:NSDateFormatterNoStyle
                                                                timeStyle:NSDateFormatterShortStyle];
      
      return stringFromDate;
  }
  
  
  // Returns the short date and time as a string
  + (NSString *)getDateAndTimeShortString:(NSDate *)date {
      
      NSString *stringFromDate = [NSDateFormatter localizedStringFromDate:date
                                                                dateStyle:NSDateFormatterShortStyle
                                                                timeStyle:NSDateFormatterShortStyle];
      
      return stringFromDate;
  }
  

To use the new methods

Make the methods available in the class

• Import the CommonMethods.h file into the class where you want to use the method
• Insert the following line under the existing #import statement

  #import "lpCommonMethods.h"

Call the methods

• Use the following syntax to display the date and time in short format set by the user

  self.startDateLabel.text = [CommonMethods getDateAndTimeShortString:self.startDate];

  where
  startDateLabel is a label on the view
  startDate is the NSDate object