iOS 获取UILabel每行的字符串

- (NSArray *)linesAtWidth:(CGFloat)width {
    if (self.text == nil) {
        return nil;
    }
    
    NSMutableAttributedString *attStr = [[NSMutableAttributedString alloc] initWithString:self.text];
    NSMutableParagraphStyle *paragraphStyle = [[NSMutableParagraphStyle alloc] init];
    paragraphStyle.lineBreakMode = NSLineBreakByWordWrapping;
    [attStr addAttribute:NSParagraphStyleAttributeName value:paragraphStyle range:NSMakeRange(0, attStr.length)];
    
    CTFontRef myFont = CTFontCreateWithName((CFStringRef)([self.font fontName]), [self.font pointSize], NULL);
    [attStr addAttribute:(NSString *)kCTFontAttributeName
                   value:(__bridge id)myFont
                   range:NSMakeRange(0, attStr.length)];
    CFRelease(myFont);
    
    CTFramesetterRef frameSetter = CTFramesetterCreateWithAttributedString((CFAttributedStringRef)attStr);
    CGMutablePathRef path = CGPathCreateMutable();
    CGPathAddRect(path, NULL, CGRectMake(0, 0, width, CGFLOAT_MAX));
    CTFrameRef frame = CTFramesetterCreateFrame(frameSetter, CFRangeMake(0, 0), path, NULL);
    NSArray *lines = (NSArray *)CTFrameGetLines(frame);
    NSMutableArray *linesArray = [[NSMutableArray alloc] init];
    for (id line in lines) {
        CTLineRef lineRef = (__bridge  CTLineRef)line;
        CFRange lineRange = CTLineGetStringRange(lineRef);
        NSRange range = NSMakeRange(lineRange.location, lineRange.length);
        NSString *lineString = [self.text substringWithRange:range];
        [linesArray addObject:lineString];
    }
    CGPathRelease(path);
    CFRelease(frame);
    CFRelease(frameSetter);
    return linesArray;
}