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