AutoLayout + RTL + UILabel text alignment

Question

I\'m finally getting round to wrestling with Auto Layout and can\'t seem to figure out how to get right-to-left (RTL) support to work the way I\'d expect/want...

I h

Answer 1

@Aviel answer as a swift 4 UILabel extension

extension UILabel {
    func decideTextDirection () {
        let tagScheme = [NSLinguisticTagScheme.language]
        let tagger    = NSLinguisticTagger(tagSchemes: tagScheme, options: 0)
        tagger.string = self.text
        let lang      = tagger.tag(at: 0, scheme: NSLinguisticTagScheme.language,
                                          tokenRange: nil, sentenceRange: nil)

        if lang?.rawValue.range(of: "he") != nil ||  lang?.rawValue.range(of: "ar") != nil {
            self.textAlignment = NSTextAlignment.right
        } else {
            self.textAlignment = NSTextAlignment.left
        }
    }
}

usage

label.text = "كتابة باللغة العربية" // Assign text
label.decideTextDirection()          // Decide direction

Answer 2

Here is my version. It's simpler and also handles multiple languages in the source document.

The Main point is to use the dominantLanguage:

let lang = tagger.dominantLanguage

Code Snippet:

 extension UILabel {
    func determineTextDirection () {
        guard self.text != nil else {return}

        let tagger = NSLinguisticTagger(tagSchemes: [.language], options: 0)
        tagger.string = self.text

        let lang = tagger.dominantLanguage

        let rtl = lang == "he" || lang == "ar"

        self.textAlignment = rtl ? .right : .left
    }
}

Usage:

titleLabel.text = "UILabel היפוך שפה עבור"
titleLabel.determineTextDirection()

Finally: Note that if the App is localized and you may rely on the phones language - the solution your after is: "Natural Text Alignment for RTL": i.e:

titleLabel.textAlignment = .natural

Use the NSLinguisticTagger when your app shows multiple lines with different languages. or when you allow free search in any language, regardless of the local.

Answer 3

You want NSTextAlignmentNatural. That infers the text alignment from the loaded application language (not from the script).

For iOS 9 and later (using Xcode 7), you can set this in the storyboard (choose the --- alignment option). If you need to target earlier releases, you'll need to create an outlet to the label and set the alignment in awakeFromNib.

- (void)awakeFromNib {
    [[self label] setTextAlignment:NSTextAlignmentNatural];
}

Answer 4

You can use MyLinearLayout to easy support RTL and LRT.

Answer 5

For me those solutions didn't help, and I ended up doing something pretty ugly but it's the only one that did the trick for me. I added it as an NSString category:

NSString+Extras.h:

#import <Foundation/Foundation.h>

@interface NSString (Extras)
- (NSTextAlignment)naturalTextAligment;
@end

NSString+Extras.m:

#import "NSString+Extras.h"

@implementation NSString (Extras)

- (NSTextAlignment)naturalTextAligment {
    NSArray *tagschemes = [NSArray arrayWithObjects:NSLinguisticTagSchemeLanguage, nil];
    NSLinguisticTagger *tagger = [[NSLinguisticTagger alloc] initWithTagSchemes:tagschemes options:0];
    [tagger setString:self];
    NSString *language = [tagger tagAtIndex:0 scheme:NSLinguisticTagSchemeLanguage tokenRange:NULL sentenceRange:NULL];
    if ([language rangeOfString:@"he"].location != NSNotFound || [language rangeOfString:@"ar"].location != NSNotFound) {
        return NSTextAlignmentRight;
    } else {
        return NSTextAlignmentLeft;
    }
}
@end

To detect the language I used this SO answer.

Answer 6

@Aviel answer as a swift UILabel extension

//MARK: UILabel extension
extension UILabel {
    func decideTextDirection () {
        let tagScheme = [NSLinguisticTagSchemeLanguage]
        let tagger    = NSLinguisticTagger(tagSchemes: tagScheme, options: 0)
        tagger.string = self.text
        let lang      = tagger.tagAtIndex(0, scheme: NSLinguisticTagSchemeLanguage,
            tokenRange: nil, sentenceRange: nil)

        if lang?.rangeOfString("he") != nil ||  lang?.rangeOfString("ar") != nil {
            self.textAlignment = NSTextAlignment.Right
        } else {
            self.textAlignment = NSTextAlignment.Left
        }
    }
}

How to use it ?

label.text = "كتابة باللغة العربية" // Assign text
label.decideTextDirection()          // Decide direction