"C.T. Matsumoto" <c.t.matsum...@gmail.com> wrote
First I've got a db class
class DB(object):
""" This does all the database handling.
"""
That's fine.
Then I've got a class to filter a list of potential tables to be
compared.
These tables need to be tested.
OK, Could that be a method of your database?
class CompareTableList(DB):
""" Make a master list, from a source list of compare tables
that need to be compared.
If the tables in the list pass the tests make a CompareItem.
Store all the CompareItems in a compare_list.
"""
I still think that from an OOP sense it would be m,ore logical to
have a Table cklass that knows hhow to compare itself to another table.
You are trying to build an object which is a function, thats rarely
a good idea. You wind up with the worst of procedural and OOP
worlds coming together.
CompareItem is the class in question.
CompareItem(object):
def __init__(self, ref_table, ref_dburi, ref_rows, test_table,
test_dburi, test_rows, keys):
...
...
This would be your suggested TestTable only it already has the pair and
is
ready to be compared. Rather than a method compare is a class.
I suspect thats your problem. cComparing things is normally an
operation of a class not a class in its own right. A compare class
would need to inspect the internal details of at least 2 objects.
But objects should manage their own data not expose it to third parties.
So either you have to pass in all the object attributes you want to know
about - long parameter lists or you pass in two objects and violate data
hiding within the comparison.
Compare(CompareTableList):
""" Foreach CompareItem in the CompareTableList.compare_list. Workout
the differences and store difference in something that can format
a report.
"""
Again this looks like a method of your database.
db.compare(tables)
foreach table in tables:
if table.compare(masterTable?):
storeDifferences()
or
db.compare(table_sets):
for table1, table2 in table_sets:
if table1.compare(table2)
storeDifferences()
Or similar.
By trying to create objects which are functions instead of making
the function a method of the objects that they act on you are
complicating your code.
--
Alan Gauld
Author of the Learn to Program web site
http://www.alan-g.me.uk/
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