iOS字符串大小转换

NSString *test = @"Hello World";  
     
   // 小写  
   NSString *lower = [test lowercaseString];  
     
   // 大写  
   NSString *upper = [lower uppercaseString];  
    
     
   NSLog(@"test: %@",lower);  
   NSLog(@"test: %@",upper);