NSString Extensions.

NSString+RAFExtensions.h

#import <Foundation/Foundation.h>

@interface NSString (RAFExtensions)

/**
 Returns random alphanumeric string with a given length.
*/
+ (NSString *)randomStringWithLength:(NSUInteger)length;

/**
 Returns YES if the string is a valid email address of form: example@example.com
*/
- (BOOL)isValidEmailString;

@end

NSString+RAFExtensions.m

#import "NSString+RAFExtensions.h"

@implementation NSString (RAFExtensions)


#pragma mark - Random string


+ (NSString *)randomStringWithLength:(NSUInteger)length
{
    NSString *letters = @"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
    NSMutableString *randomString = [NSMutableString stringWithCapacity:length];
    
    for (int i = 0; i < length; i++)
    {
        [randomString appendFormat:@"%C", [letters characterAtIndex:arc4random() % [letters length]]];
    }
    
    return randomString;
}


#pragma mark - Email validation
 
 
- (BOOL)isValidEmailString
{
    NSString *emailRegex = @"[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,4}";
    NSPredicate *emailTest = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", emailRegex];
    
    return [emailTest evaluateWithObject:self];
}


@end