Asynchronous image downloading with dispatch_async queue

Hi,

There's no need to implement any framework for LazyImage loading as of now. You can do it simply by writing few lines of code below.. Just take a look..


Example : 

UIActivityIndicatorView *activity = [[UIActivityIndicatorView alloc]init];
UIImageView * userImage = [[UIImageView alloc]init];

        [activity startAnimating];

        dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0ul);

        dispatch_async(queue, ^(void) {

            //  You may want to cache this explicitly instead of reloading every time.

            NSData *imageData = [NSData dataWithContentsOfURL:[NSURL URLWithString:url]];

            UIImage* image = [[UIImage alloc] initWithData:imageData];

            dispatch_async(dispatch_get_main_queue(), ^{

                // Capture the indexPath variable, not the cell variable, and use that

               userImage.image = image;

                [activity stopAnimating];

            });

       });

Regards,

Nilesh M. Prajapati

NSData to HexString and HexString to NSData

Hi everyone,
Here, I've put two different methods for the conversion of "HEXString" to "NSData" and "NSData" to "HEXString".  you may get help from these two. Please ask if you have any query.


- (NSData *)dataFromHexString:(NSString *)string
{  
    NSMutableData *stringData = [[[NSMutableData alloc] init] autorelease];
    unsigned char whole_byte;
    char byte_chars[3] = {'\0','\0','\0'};
    int i;
    for (i=0; i < [string length] / 2; i++) {
        byte_chars[0] = [string characterAtIndex:i*2];
        byte_chars[1] = [string characterAtIndex:i*2+1];
        whole_byte = strtol(byte_chars, NULL, 16);
        [stringData appendBytes:&whole_byte length:1];
    }
    return stringData;
}

- (NSString*)hexStringFromData:(NSData *)data
{
    unichar* hexChars = (unichar*)malloc(sizeof(unichar) * (data.length*2));
    unsigned char* bytes = (unsigned char*)data.bytes;
    for (NSUInteger i = 0; i < data.length; i++) {
        unichar c = bytes[i] / 16;
        if (c < 10) c += '0';
        else c += 'a' - 10;
        hexChars[i*2] = c;
        c = bytes[i] % 16;
        if (c < 10) c += '0';
        else c += 'a' - 10;
        hexChars[i*2+1] = c;
    }
    NSString* retVal = [[NSString alloc] initWithCharactersNoCopy:hexChars
                                                           length:data.length*2
                                                     freeWhenDone:YES];
    return [retVal autorelease];
}


If any one has query then share it over here.

Thanks and Regards,
Nilesh Prajapati