Is there a way to generate QR code image on iOS

Question

Is there a standard way to generate a QR code and attach it to a mail item from iOS client app (no server code)?

Answer 1

I created a NSString Category for Obj-C, taking Mike Demidov awesome answer

NString+GGQRCode.h

#import 
#import 

@interface NSString (GGQRCode)

-(UIImage *)qrCodeImage:(CGFloat)width height:(CGFloat)height;
-(UIImage *)qrCodeImage:(CGFloat)width height:(CGFloat)height scale:(CGFloat)scale orientation:(UIImageOrientation)orientation;

@end

NString+GGQRCode.m

#import "NSString+GGQRCode.h"

@implementation NSString (GGQRCode)

-(UIImage *)qrCodeImage:(CGFloat)width height:(CGFloat)height
{
    return [self qrCodeImage:width height:height scale:[UIScreen mainScreen].scale orientation:UIImageOrientationUp];
}

-(UIImage *)qrCodeImage:(CGFloat)width height:(CGFloat)height scale:(CGFloat)scale orientation:(UIImageOrientation)orientation
{
    NSData *stringData = [self dataUsingEncoding: NSUTF8StringEncoding];

    CIFilter *qrFilter = [CIFilter filterWithName:@"CIQRCodeGenerator"];
    [qrFilter setValue:stringData forKey:@"inputMessage"];
    [qrFilter setValue:@"H" forKey:@"inputCorrectionLevel"];

    CIImage *qrImage = qrFilter.outputImage;
    float scaleX = width / qrImage.extent.size.width;
    float scaleY = height / qrImage.extent.size.height;

    qrImage = [qrImage imageByApplyingTransform:CGAffineTransformMakeScale(scaleX, scaleY)];

    return [UIImage imageWithCIImage:qrImage scale:scale orientation:orientation];
}

@end