method argument - Whole Object or individual attributes??

[Varun Chopra]

Suppose I have this class:

class User
{
   int id;
   String name;
   Date dob;
   String profession;
}

I have a Utility class with following methods:

class UserUtility
{
   List<User> scanListByName(List<User> inputList, String name)
   {
      //code
   }
 
   List<User> scanListById(List<User> inputList, int id)
   {
      //code
   }
 
   List<User> scanListByDOB(List<User> inputList, Date dob)
   {
      //code
   }
}

My question is, instead of String name/int id/Date dob - should we pass whole User object? I have seen some developers always passing the whole object instead of individual values. In such cases syntax is:

class UserUtility
{
   List<User> scanListByName(List<User> inputList, User arg)
   {
      //code
   }
 
   List<User> scanListById(List<User> inputList, User arg)
   {
      //code
   }
 
   List<User> scanListByDOB(List<User> inputList, User arg)
   {
      //code
   }
}

[Rob Spoor]

I don't see the point in passing an entire User object if all you need is one of its values.

If you get your date of birth from another source, you would have to create a User object with bogus values for the other fields.


With both approaches you can mimic the other approach:

// I have a user object and call the method with Date as parameter
// see how I can just retrieve one value from the user?
List<Users> dobUsers = scanListById(inputList, user.dob);
 
// I have a Date object and call the method with User as parameter
// see how I need bogus values to create a User object?
List<Users> dobUsers = scanListById(inputList, new User(-1, null, dob, null));

See why I'd prefer just having a Date object? Remember: you can get a Date from a User quite easily, but to get a User from a Date you need to create that new User.

[Varun Chopra]

Thanks Rob