How to call a method from outside a @implementation?

Question

This is my first try at iOS development. That being said, I am trying to md5 a password

This is my .m file

#import "SMViewController.h"
#import <CommonCrypto/CommonDigest.h> // Need to import for CC_MD5 access

@interface SMViewController ()

@end

@implementation SMViewController

.........
.........
.........

- (IBAction)buttonLoginClicked:(id)sender {
    @try {

        if([[self.textEmail text] isEqualToString:@""] || [[self.textPassword text] isEqualToString:@""] ) {
            [self alertStatus:@"Please enter both Username and Password" :@"Login Failed!"];
        } else {
            /*String parameters = parametersData + "&controler=" + user + "&function=" + login + "&json=&client_type=android_client&client_id=" + GCMRegistrar.getRegistrationId(context) + "&ver="+VER;*/
            NSString *post =[[NSString alloc] initWithFormat:@"email=%@&pass=%@&controler=user&function=login&json=&client_type=ip_client&client_id=x&ver=1321",[self.textEmail text],[self.textPassword text]];

…………………………….
………
……..
……

            }   
- (IBAction)backgroundClick:(id)sender {
    [self.textPassword resignFirstResponder];
   [self.textEmail resignFirstResponder];
}
@end





@implementation NSString (MyExtensions)
- (NSString *)md5
{
    const char *cStr = [self UTF8String];
    unsigned char result[CC_MD5_DIGEST_LENGTH];
    CC_MD5( cStr, strlen(cStr), result ); // This is the md5 call
    return [NSString stringWithFormat:
            @"%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x",
            result[0], result[1], result[2], result[3],
            result[4], result[5], result[6], result[7],
            result[8], result[9], result[10], result[11],
            result[12], result[13], result[14], result[15]
            ];
}
@end

@implementation NSData (MyExtensions)
- (NSString*)md5
{
    unsigned char result[CC_MD5_DIGEST_LENGTH];
    CC_MD5( self.bytes, self.length, result ); // This is the md5 call
    return [NSString stringWithFormat:
            @"%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x",
            result[0], result[1], result[2], result[3],
            result[4], result[5], result[6], result[7],
            result[8], result[9], result[10], result[11],
            result[12], result[13], result[14], result[15]
            ];
}
@end

my .h file:

@interface NSString (MyExtensions)
- (NSString *)md5;
@end

@interface NSData (MyExtensions)
- (NSString*)md5;
@end

How can I pass the textPassword to the md5

this is based on MD5 algorithm in Objective C

Answer 1

Since you've just created a category on NSString and NSData, you can easily call it on a string (or data) like you call any other method (for example init).

So in your case it should be like this:
[[self.textPassword text] md5]
(that will return a string containing the md5 of the textPassword.text)

Tips for your code:
Categories are usually stored in their own separate file, like NSString+MD5.h and NSString+MD5.m, with additions specified after the + sign, and then imported where needed.

Also, you should access properties through the dot syntax, eg. self.textPassword.text instead of [self.textPassword text], or at least don't mix them (because textPassword is a property of self also - you could then do [self textPassword] and it would be the same).