iOS - Combine NSLineBreakByWordWrapping and NSLineBreakByTruncatingTail

问题

What I need

I need to write some text to a PDF. The text itself can be any length, but I can only display 2 lines (by word wrapping) and should truncate the tail in the second line if the space isn't enough.

What I've tried

NSMutableParagraphStyle *text = [[NSMutableParagraphStyle defaultParagraphStyle] mutableCopy];
text.lineBreakMode = NSLineBreakByTruncatingTail;

This way, the text goes only in the first line, and truncates at the end of the line.

NSMutableParagraphStyle *text = [[NSMutableParagraphStyle defaultParagraphStyle] mutableCopy];
text.lineBreakMode = NSLineBreakByWordWrapping;

This way, the text wraps to the second line, but if there's enough text for more lines, there's no truncating at the end of the second line.

I need some way to combine these two behaviours.

What I've researched

I've found some questions about problems with word wrapping, but nothing like this. The nearest I've got was this:

NSLineBreakByWordWrapping on First Line but NSLineBreakByTruncatingTail For Second Line?

But the problem there was different. In that question, the asker wants this behaviour but in a label, and he fixes the problem with some storyboard configuration that I've also used in other part of my project. But this question is about this behaviour in a PDF, using the NSStringDrawingContext drawInRect method.

I'm using iOS 7 (actually just updated to 7.1, but the situation is the same in both).

Thanks in advance.

Edit - also, I've looked this link before asking, but with no help:

https://developer.apple.com/library/ios/documentation/cocoa/reference/ApplicationKit/Classes/NSParagraphStyle_Class/Reference/Reference.html#//apple_ref/doc/c_ref/NSLineBreakByWordWrapping

回答1:

Refer to :

@interface NSAttributedString (NSExtendedStringDrawing)
- (void)drawWithRect:(CGRect)rect options:(NSStringDrawingOptions)options context:(NSStringDrawingContext *)context NS_AVAILABLE_IOS(6_0);
- (CGRect)boundingRectWithSize:(CGSize)size options:(NSStringDrawingOptions)options context:(NSStringDrawingContext *)context NS_AVAILABLE_IOS(6_0);
@end

Pass "NSStringDrawingUsesLineFragmentOrigin | NSStringDrawingTruncatesLastVisibleLine" for options, please note this method is only available for NSAttributedString.

回答2:

Answer in Swift 4,

let str = NSMutableAttributedString(string: "long string")
str.draw(with: label.frame, options: [NSStringDrawingOptions.usesLineFragmentOrigin, .truncatesLastVisibleLine], context: nil)         
label.numberOfLines = 0
label.attributedText = str.copy() as? NSAttributedString

来源：https://stackoverflow.com/questions/22396347/ios-combine-nslinebreakbywordwrapping-and-nslinebreakbytruncatingtail