Re: ****SPAM(7.4)**** Re: ****SPAM(11.2)**** [Tutor] Larger program organization

2005-02-13 Thread Kent Johnson 
Bob Gailer wrote:
At 03:21 PM 2/12/2005, Brian van den Broek wrote:
[snip]
 > I am curious about Bob's "Whenever you find yourself writing
 > an if statement ask whether this would be better handled by subclasses."
class A:
...
class A1(A);
  def foo(self, ...):
statements to process object of type 1
class A2(A);
  def foo(self, ...):
statements to process object of type 2
That takes less code. Eliminates the type property. I get greater 
visibility about the existence and distinction of the two (or more) 
sub-types. I now can much more easily extend each subtype.
Also you can more easily *add* a new subtype. Using if statements, if you add a new type you have to 
find all the relevant conditionals and add another condition. With subclassing, you create a new 
subclass and define the necessary methods. The changes are localized to the subclass and much easier 
to figure out.

Kent
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Re: ****SPAM(7.4)**** Re: ****SPAM(11.2)**** [Tutor] Larger program organization

2005-02-13 Thread Bob Gailer 
At 03:21 PM 2/12/2005, Brian van den Broek wrote:
[snip]
> I am curious about Bob's "Whenever you find yourself writing
> an if statement ask whether this would be better handled by subclasses."
I start out writing a class like:
class A:
  def __init__(self, type):
self.type = type
...
  def foo(self, ...):
if self.type = 1:
  statements to process object of type 1
else:
  statements to process object of type 2
The '"if statement" alerts me to consider creating subclasses for types 1 
and 2:

class A:
...
class A1(A);
  def foo(self, ...):
statements to process object of type 1
class A2(A);
  def foo(self, ...):
statements to process object of type 2
That takes less code. Eliminates the type property. I get greater 
visibility about the existence and distinction of the two (or more) 
sub-types. I now can much more easily extend each subtype.

Bob Gailer
mailto:[EMAIL PROTECTED]
303 442 2625 home
720 938 2625 cell 

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