Re: reduce redundant code


"Ralph" <nt_consulting64@xxxxxxxxx> wrote in message
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"MP" <NoSpam@xxxxxxxxxx> wrote in message
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Is there any merit to the following idea?

I find myself repeating lines similar to below in many routines
the idea being I may want to process all objects of just objects who have
certain property or whose "container" or "owner" or "child" has certain
property(ies)
snip
thanks for any comments
mark


Your actually chewing on several things at once here.
Get Fowler's book "Refactoring: Improving the Design of Existing Code".
Impossible to give a specific answer as it depends on the over-all object
of
your design.
Hints: (???? no idea of this is useful or not. <g>)
Whenever you find yourself with a ton of parameters, think object.
If only certain objects of a specific type support something, why not it
let
the object handle it or ignore it?
"Filters" are usually only concerned with bags of stuff. Make it a
propery/method of the Bag.

-ralph

Hi Ralph,
re: your quote
"Filters" are usually only concerned with bags of stuff.

in my case the bag of stuff is the api of the external program my utils
"interact with"
that bag has lots of kinds of objects

the api presents a collection of all the objects in that file from which I
want to select

example
appA wants to look at objects containing text data
(but only if they also match certain secondary lists of properties)

so in my current/older code all my routines have to do something like

For Each obj In Bag
'primary test...object type
'only want objs of certain group of types
If TypeOf obj is x
Or If TypeOf obj is y
Or If TypeOf obj is z then
'obj type ok

'secondary test...other properties of interest
'now only objs w/ certain props are of interest in this case so...
if obj.Propa = a and obj.Propb = b and obj.Propc = c etc then
'do obj

Next

that kind of multiple branches of tests litter my code everywhere
everytime i write another routine to look at certain things i have to
rewrite that group of tests with current values..

so what I came up with so far, based on amdrits suggestion is
IFilter (interface to test for object type and list of secondary
properties)
cTextFilter(Implements IFilter for objects of types that can contain textual
data)
cTextVal - an object that can contain a textual value

Sub Routine1()
'create textfilter object
Dim oTF as IFilter
Set oTF = New cTextFilter
'set secondary properties
oTf.PropA = a : oTf.PropB= B oTf.PropC= c:

'create textvalue object that extracts/updates text value in object
containing text
Dim oTV as cTextVal
Set oTv = New cTextVal

'apply current filterObject to TextualObject
'strategy??? 'aggregation??? 'composition???
set oTv.ObjectFilter = oTf

'now loop becomes

For Each obj In Bag
if oTv.IsValidObject(obj) Then
'do oTv.SourceObject
End If
Next

'pseudo code classes
IFilter class(interface)
Option Explicit

Public Property Get IsValidObject(obj As Object) As Boolean
'allow implementations test validity of input
End Property

'VariousOtherProperties
Public Property Get PropA() As String
End Property

Public Property Get PropB() As String
End Property
'etc

'cTextFilter
Implements IFilter
'type of filter for objects which can contain textual data
Private Property Get IFilter_IsValidObject(obj As Object) As Boolean
'test for objects that can contain a textual value
End Property

'cTextVal
'object that has textual data
Property Set ObjectFilter(obj as cTextFilter)
Set moFilter = obj
Property Get IsValidObject(obj as object) As Boolean
If moFilter.IsValidObject(obj) Then
IsValidObject = True
Set moSourceObject = obj
End If
End Property
Property Get SourceObject()as Object



do I have it all assbackwards?
:-)
Thanks mark


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