iOS NSString追加字符串的方法

 NSArray *array = [NSArray arrayWithObjects:@"Hello",@" ",@"world", @"!", nil];
 NSString *printStr = @"";
 for(int i = 0; i < [array count]; i++){
     printStr = [printStr stringByAppendingFormat:@"%@", [array objectAtIndex:i]];
 }
 NSLog(@"第一种方法%@", printStr);

 NSArray *array = [NSArray arrayWithObjects:@"Hello",@" ",@"world", @"!", nil];
 NSMutableString *printStr2 = [[NSMutableString alloc] init];
 for(int i = 0; i < [array count]; i++){
      [printStr2 appendFormat:@"%@", [array objectAtIndex:i]];
 }
 NSLog(@"第二种方法%@", printStr2);

2015-06-01 21:33:52.964 String追加字符串[28638:601104] 第一种方法Hello world!
2015-06-01 21:33:52.965 String追加字符串[28638:601104] 第二种方法Hello world!