* 中英文混合字符串截取

- (NSString *)subStringByByteWithIndex:(NSInteger)index {
  NSInteger sum = 0;
  NSString *sourceStr = @"";
  NSString *subStr = [[NSString alloc] init];

  for(int i = 0; i<[sourceStr length]; i++) {
      unichar strChar = [sourceStr characterAtIndex:i];
      if(strChar < 256) {
        sum += 1; 
      } else {
        sum += 2;
      }
      if (sum >= index) {
        subStr = [sourceStr substringToIndex:i+1];
        return subStr;
      }   
   }
    return subStr;
  }

* 獲取字符串字節(jié)數(shù)

 - (int)getByteNum:(NSString *)string {
    int strlength = 0;
    char* p = (char*)[string cStringUsingEncoding:NSUnicodeStringEncoding];

    for (int i=0 ; i<[string lengthOfBytesUsingEncoding:NSUnicodeStringEncoding] ;i++) {
        if (*p) {
          p++;
          strlength++;
        } else {
          p++;
        }
     }
    return strlength;
 }

* 多行字符串，最后一行的中間處省略多余字符

  UILabel *txtLabel = [[UILabel alloc] init];
  txtLabel.frame = CGRectMake(15, 460, 345, 100);
  txtLabel.numberOfLines = 2;
  txtLabel.backgroundColor = [UIColor cyanColor];
  [self.view addSubview:txtLabel];

  NSMutableAttributedString *attrStr = [[NSMutableAttributedString alloc] initWithString:@"上海東方明珠廣播電視塔上海東方明珠廣播電視塔上海東方明珠廣播電視塔上海東方明珠廣播電視塔上海東方明珠廣播電視塔上海東方明珠廣播電視塔"];
  NSMutableParagraphStyle *paraph =  [[NSMutableParagraphStyle alloc] init];
  paraph.baseWritingDirection = NSWritingDirectionRightToLeft;
  paraph.headIndent = 120;
  [attrStr addAttribute:NSParagraphStyleAttributeName value:paraph range:NSMakeRange(0, attrStr.length)];
  txtLabel.attributedText = attrStr;
  txtLabel.lineBreakMode = NSLineBreakByTruncatingTail;

屏幕快照 2018-09-18 下午5.17.59.png