NSString category (Objective C) and String extension (Swift) to format date

NSString+DateFormatter.h

#import <Foundation/Foundation.h>

@interface NSString (DateFormatter)

- (NSString *)dateStringFromFormat:(NSString *)fromFormat toFormat:(NSString *)toFormat;

@end

NSString+DateFormatter.m

//http://www.alexcurylo.com/2009/01/28/nsdateformatter-formatting/

#import "NSString+DateFormatter.h"

@implementation NSString (DateFormatter)

- (NSString *)dateStringFromFormat:(NSString *)fromFormat toFormat:(NSString *)toFormat{
    NSDateFormatter *fromFormatter = [[NSDateFormatter alloc]init];
    [fromFormatter setDateFormat:fromFormat];
    
    NSDate *fromDate = [fromFormatter dateFromString:self];
    
    NSDateFormatter *toFormatter = [[NSDateFormatter alloc]init];
    [toFormatter setDateFormat:toFormat];
    
    
    return [toFormatter stringFromDate:fromDate];
}
@end

TDateFormattingString.swift

extension String{
    func dateStringFromFormat (fromFormat:String, toFormat:String) -> String{
        let fromFormatter:NSDateFormatter = NSDateFormatter()
        fromFormatter.dateFormat = fromFormat
        
        let fromDate:NSDate? = fromFormatter.dateFromString(self)
        
        let toFormatter:NSDateFormatter = NSDateFormatter()
        toFormatter.dateFormat = toFormat
        
        if let date = fromDate{
            return toFormatter.stringFromDate(date)
        }
        return ""
        
    }
}