NSString根据宽度获得能显示出的字符串

- (NSString *)getVisibleStringWithWidth:(CGFloat)width font:(UIFont *)font {

NSMutableParagraphStyle *p = [[NSMutableParagraphStyle alloc] init];

p.lineBreakMode = NSLineBreakByCharWrapping;

NSAttributedString *namesAtt = [[NSAttributedString alloc] initWithString:self attributes:@{NSFontAttributeName:font, NSParagraphStyleAttributeName:p}];

CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString((CFAttributedStringRef)namesAtt);

UIBezierPath *path = [UIBezierPath bezierPathWithRect:CGRectMake(0, 0, width, 25.)];

CTFrameRef frame = CTFramesetterCreateFrame(framesetter, CFRangeMake(0, self.length), path.CGPath, NULL);

CFRange range = CTFrameGetVisibleStringRange(frame);

CFRelease(framesetter);

CFRelease(frame);

return [self substringWithRange:NSMakeRange(range.location, range.length)];

}