Label Alignment in iOS 6 - UITextAlignment deprecated

Question

In iOS6 you can use

label.textAlignment = NSTextAlignmentCenter;

The labelAlignment property change is probably related to Apple’s introducing NSAttributedStrings to more of the iOS controls, and therefore needing to change the UIText… properties to NSText… properties.

So if you’ve upgraded to iOS6, you’re in clover; just switch from UITextAlignmentCenter to NSTextAlignmentCenter and enjoy the fancy new strings.

But if you’re working with a complex project and would prefer that the earth not move so much under your feet, you might want to stick with an older version for a while, and adapt your code for multiple versions, something like this:

// This won't compile:
if ([label respondsToSelector:@selector(attributedText:)]) 
    label.textAlignment = UITextAlignmentCenter;
else 
    label.textAlignment = NSTextAlignmentCenter;

The above approach works for new methods; you get warnings but everything runs fine. But when the compiler sees a constant that it doesn’t know about, it turns red and stops in its tracks. There’s no way to sneak NSTextAlignmentCenter past it. (Well, there might be a way to customize the compiler’s behavior here, but it seems inadvisable.)

The workaround is to add some conditional preprocessor defines. If you put something like this in your class’s h file (or perhaps in an imported constants file -- which must itself include #import <UIKit/UIKit.h> in order to ever know about the NSText... constants)…

#ifdef NSTextAlignmentCenter // iOS6 and later
#   define kLabelAlignmentCenter    NSTextAlignmentCenter
#   define kLabelAlignmentLeft      NSTextAlignmentLeft
#   define kLabelAlignmentRight     NSTextAlignmentRight
#   define kLabelTruncationTail     NSLineBreakByTruncatingTail 
#   define kLabelTruncationMiddle   NSLineBreakByTruncatingMiddle
#else // older versions
#   define kLabelAlignmentCenter    UITextAlignmentCenter
#   define kLabelAlignmentLeft      UITextAlignmentLeft
#   define kLabelAlignmentRight     UITextAlignmentRight
#   define kLabelTruncationTail     UILineBreakModeTailTruncation
#   define kLabelTruncationMiddle   UILineBreakModeMiddleTruncation
#endif

…you can do this:

label.textAlignment = kLabelAlignmentCenter;

And this:

label.lineBreakMode = kLabelTruncationMiddle;

Etc.

Since these UIText/NSText changes are likely to be popping up for multiple controls, this approach is quite handy.

(Caveat: Being a member of the aforementioned steady-earth lovers, I have tested this with an old version, but not yet with iOS6.)

NSTextAlignmentCenter can be used in place of UITextAlignmentCenter and a list of other replacements is below:

#ifdef __IPHONE_6_0 // iOS6 and later
#   define UITextAlignmentCenter    NSTextAlignmentCenter
#   define UITextAlignmentLeft      NSTextAlignmentLeft
#   define UITextAlignmentRight     NSTextAlignmentRight
#   define UILineBreakModeTailTruncation     NSLineBreakByTruncatingTail
#   define UILineBreakModeMiddleTruncation   NSLineBreakByTruncatingMiddle
#endif

#if (__IPHONE_OS_VERSION_MIN_REQUIRED >= __IPHONE_6_0)
# define ALIGN_CENTER NSTextAlignmentCenter
#else
# define ALIGN_CENTER UITextAlignmentCenter
#endif

UILabel* label = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 50, 30)];
label.text = @"There is no spoon";
label.textAlignment = ALIGN_CENTER;
[self addSubview:label];

You don't have to do either of these. Xcode 4.5 will compile the NSTextAlignmentCenter, etc. fine in iOS 5.