How do I get word wrap information with the new iOS 7 APIs?

Question

I noticed that iOS 7 introduces new classes related to text layout such as NSLayoutManager, NSTextStorage, and NSTextContainer. How can I use these in order to get information about word wrapping on an NSString?

For example, say I have a long NSString which I put in a UILabel. If I enable multiple lines on the UILabel, it would produce a string such as the following:

The quick brown fox jumps
over the lazy dog.

That's great, but I can't access the line breaks in code (e.g. after the word jumps I would want it to return \n or something similar). I would want to know at which character indexes the line breaks occur. I know we can do this with CoreText, but since we have these new classes in iOS 7, I was wondering how we can use them instead.

Answer 1

Example:

CGFloat maxWidth = 150;
NSAttributedString *s = 
    [[NSAttributedString alloc] 
        initWithString:@"The quick brown fox jumped over the lazy dog." 
        attributes:@{NSFontAttributeName:[UIFont fontWithName:@"GillSans" size:20]}];
NSTextContainer* tc = 
    [[NSTextContainer alloc] initWithSize:CGSizeMake(maxWidth,CGFLOAT_MAX)];
NSLayoutManager* lm = [NSLayoutManager new];
NSTextStorage* tm = [[NSTextStorage alloc] initWithAttributedString:s];
[tm addLayoutManager:lm];
[lm addTextContainer:tc];
[lm enumerateLineFragmentsForGlyphRange:NSMakeRange(0,lm.numberOfGlyphs) 
    usingBlock:^(CGRect rect, CGRect usedRect, 
                 NSTextContainer *textContainer, 
                 NSRange glyphRange, BOOL *stop) {
    NSRange r = [lm characterRangeForGlyphRange:glyphRange actualGlyphRange:nil];
    NSLog(@"%@", [s.string substringWithRange:r]);
}];

Answer 2

swift translation:

    guard let font1: UIFont = textView.font else { return }
    var lines: [String] = []

    let maxWidth: CGFloat = textView.frame.width
    let s: NSAttributedString = NSAttributedString.init(string: textView.text, attributes: [.font: font1])
    let tc: NSTextContainer = NSTextContainer.init(size: CGSize(width: maxWidth, height: CGFloat.greatestFiniteMagnitude))
    let lm: NSLayoutManager = NSLayoutManager.init()
    let tm: NSTextStorage = NSTextStorage.init(attributedString: s)
    tm.addLayoutManager(lm)
    lm.addTextContainer(tc)
    lm.enumerateLineFragments(forGlyphRange: NSRange(location: 0, length: lm.numberOfGlyphs)) { (rect: CGRect, usedRect: CGRect, textContainer: NSTextContainer, glyphRange: NSRange, Bool) in

        let r: NSRange = lm.characterRange(forGlyphRange: glyphRange, actualGlyphRange: nil)

        let str = s as NSAttributedString

        let s2 = str.attributedSubstring(from: r)

        print(s2)

        lines.append(s2.string)

    }