[Tutor] Design - Granularity of classes

[Alexandre Ratti]

Hello,


How granular do you make your classes? I.e. do you usually wrap fairly 
simple data in classes? Here is an example.

Let's assume we upload files into a Web app. Let's call UploadFile the 
class that is used to handle these files. UploadFile will hold properties 
such as size and type.


class UploadFile:
     """Uploaded file."""

     def __init__(self, name, data, size, type):
         self.name = name
         self.data = data
         self.size = size
         self.type = type
         # etc

For instance, would you create a FileType class to hold the mime type and a 
FileSize class to hold the type?


class FileType:
     """File type"""

     def __init__(self, type):
         # Can test mime type here
         self.type = type

     def __repr__(self):
         return str(self.type)


class FileSize:
     """File size"""

     def __init__(self, size):
         # Can test data type here
         self.size = size

     def __repr__(self):
         return str(self.size)

Now UploadFile could be rewritten as:


class UploadFile2:
     """Uploaded file."""

     def __init__(self, name, data, size, type):
         self.name = name
         self.data = data
         self.size = FileSize(size)
         self.type = FileType(type)
         # etc

=> Does it make sense? I think this strategy would add overhead but it 
might help testing for correct data type.



Thanks.

Alexandre