UIAlertView/UIAlertController iOS 7 and iOS 8 compatibility

Question

I am using Swift to write an app and I need to show an alert. The app must be iOS 7 and iOS 8 compatible. Since UIAlertView has been replaced with UIAlert

Answer 1

You could use a category to solve that (though you'll need to convert it to Swift):

@implementation UIView( AlertCompatibility )

+( void )showSimpleAlertWithTitle:( NSString * )title
                          message:( NSString * )message
                cancelButtonTitle:( NSString * )cancelButtonTitle
{
    if( [[UIDevice currentDevice] isSystemVersionLowerThan: @"8"] )
    {
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle: title
                                                        message: message
                                                       delegate: nil
                                              cancelButtonTitle: cancelButtonTitle
                                              otherButtonTitles: nil];
        [alert show];
    }
    else
    {
        // nil titles break alert interface on iOS 8.0, so we'll be using empty strings
        UIAlertController *alert = [UIAlertController alertControllerWithTitle: title == nil ? @"": title
                                                                       message: message
                                                                preferredStyle: UIAlertControllerStyleAlert];

        UIAlertAction *defaultAction = [UIAlertAction actionWithTitle: cancelButtonTitle
                                                                style: UIAlertActionStyleDefault
                                                              handler: nil];

        [alert addAction: defaultAction];

        UIViewController *rootViewController = [UIApplication sharedApplication].keyWindow.rootViewController;
        [rootViewController presentViewController: alert animated: YES completion: nil];
    }
}

@end

@implementation UIDevice( SystemVersion )

-( BOOL )isSystemVersionLowerThan:( NSString * )versionToCompareWith
{
    if( versionToCompareWith.length == 0 )
        return NO;

    NSString *deviceSystemVersion = [self systemVersion];
    NSArray *systemVersionComponents = [deviceSystemVersion componentsSeparatedByString: @"."];

    uint16_t deviceMajor = 0;
    uint16_t deviceMinor = 0;
    uint16_t deviceBugfix = 0;

    NSUInteger nDeviceComponents = systemVersionComponents.count;
    if( nDeviceComponents > 0 )
        deviceMajor = [( NSString * )systemVersionComponents[0] intValue];
    if( nDeviceComponents > 1 )
        deviceMinor = [( NSString * )systemVersionComponents[1] intValue];
    if( nDeviceComponents > 2 )
        deviceBugfix = [( NSString * )systemVersionComponents[2] intValue];


    NSArray *versionToCompareWithComponents = [versionToCompareWith componentsSeparatedByString: @"."];

    uint16_t versionToCompareWithMajor = 0;
    uint16_t versionToCompareWithMinor = 0;
    uint16_t versionToCompareWithBugfix = 0;

    NSUInteger nVersionToCompareWithComponents = versionToCompareWithComponents.count;
    if( nVersionToCompareWithComponents > 0 )
        versionToCompareWithMajor = [( NSString * )versionToCompareWithComponents[0] intValue];
    if( nVersionToCompareWithComponents > 1 )
        versionToCompareWithMinor = [( NSString * )versionToCompareWithComponents[1] intValue];
    if( nVersionToCompareWithComponents > 2 )
        versionToCompareWithBugfix = [( NSString * )versionToCompareWithComponents[2] intValue];

    return ( deviceMajor < versionToCompareWithMajor )
           || (( deviceMajor == versionToCompareWithMajor ) && ( deviceMinor < versionToCompareWithMinor ))
           || (( deviceMajor == versionToCompareWithMajor ) && ( deviceMinor == versionToCompareWithMinor ) && ( deviceBugfix < versionToCompareWithBugfix ));
}

@end

Then just call

[UIView showSimpleAlertWithTitle: @"Error" message: message cancelButtonTitle: @"OK"];

But, if you do not want to check the system version, just use

BOOL lowerThaniOS8 = NSClassFromString( @"UIAlertController" ) == nil;

inside the category UIView( AlertCompatibility )