seven data members

gozlemci · 12-01-2010, 05:49 AM

Hi There;
I've read "Code Complete" and the Author mentioned a principle :
"Be critical of classes that contain more than about seven data members"

There is a point that I can not understand is "data member". Is he mentioned a class that contains seven different type of variables, or seven variables in same type?
I mean, according to author, which class must I take care, Class1 or Class2 below?

Code:

public class Class1 
{

type1 var1
type2 var2
type3 var3
type4 var4
type5 var5
type6 var6
type6 var7

}

Code:

public class Class2
{
type1 var1,var2,var3,var4,var5,var6,var7
}

Thanks in advance.

graemef · 12-01-2010, 07:25 AM

both (according to the author)

eSelix · 12-01-2010, 07:28 AM

I can not agree with this assumption. Every class should have that many data members as much as it needs.

graemef · 12-01-2010, 08:04 AM

Quote:

Originally Posted by eSelix

I can not agree with this assumption. Every class should have that many data members as much as it needs.

I agree with you but I think that the idea (which has some merit) is that if a class has more than a certain number of data members then you should question the class to see if it should be broken down into sub classes. Often that leads to moving the complexity out of the class and into the hierarchy.

rupertwh · 12-01-2010, 08:25 AM

Quote:

Originally Posted by eSelix

Every class should have that many data members as much as it needs.

Yes, but the original auther's point is to question that need. Or, more exactly, to give a hint as to when to question that need.

Which is very reasonable, just as a lot of indenting levels or very long functions are signs that a function probably better be divided into smaller units. (see charper 1 and 6 of Linux coding style guidelines).