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<DIV> <A title=alemartinez2112@gmail.com
href="mailto:alemartinez2112@gmail.com">Alejandro Martínez</A><FONT face=Arial
size=2> wrote:</FONT><BR></DIV>
<BLOCKQUOTE
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV>Hello list. I'm searching for the opinion of experienced
developers:<BR><BR>In which case do you create specialized class message for
instantiating an object?<BR><BR>I think two factors are fundamental:<BR>1) You
want to enforce correcteness of your objects by making sure they are complete,
so you "minimize" #new and provide specialized messages for creation. <BR>2)
You do not want to enforce anything until real usage experience shows you
which messages you must "promote" to the class side.<BR></DIV></BLOCKQUOTE>
<DIV><FONT face=Arial size=2>Point 1 is indeed fundamental: Specialized instance
creation methods are</FONT></DIV>
<DIV><FONT face=Arial size=2>used to create fully initialized instances.
Beautiful examples of that</FONT></DIV>
<DIV><FONT face=Arial size=2>approach can be found mainly in the old parts of
Squeak. Have a</FONT></DIV>
<DIV><FONT face=Arial size=2>look e.g. at</FONT></DIV>
<DIV><FONT face=Arial size=2> PluggableListView<BR>
PluggableButtonView<BR> PluggableTextView<BR>
PopUpMenu<BR> SelectionMenu</FONT></DIV>
<DIV><FONT face=Arial size=2>or at classes Browser and
Inspector.</FONT></DIV>
<DIV><FONT face=Arial size=2>PluggableListView has one general class method that
creates</FONT></DIV>
<DIV><FONT face=Arial size=2>a fully initialized instance. That method is also
sent by two</FONT></DIV>
<DIV><FONT face=Arial size=2>simpler class methods that provide reasonable
default values</FONT></DIV>
<DIV><FONT face=Arial size=2>for unneeded features of an instance.</FONT></DIV>
<DIV><FONT face=Arial size=2>In PopUpMenu a general class method is
#labelArray:lines:</FONT></DIV>
<DIV><FONT face=Arial size=2>its simplified variant is #labelArray:</FONT></DIV>
<DIV><FONT face=Arial size=2>All the classes that I just mentioned provide
both general</FONT></DIV>
<DIV><FONT face=Arial size=2>and specialized class methods for instance
creation.</FONT></DIV>
<DIV><FONT face=Arial size=2>That approach is, in my opinion, an example of
careful</FONT></DIV>
<DIV><FONT face=Arial size=2>class design that </FONT><FONT face=Arial
size=2>should be followed. I agree however</FONT></DIV>
<DIV><FONT face=Arial size=2>that some additional work is needed to find out
required</FONT></DIV>
<DIV><FONT face=Arial size=2>initial values and suitable default values for
features</FONT></DIV>
<DIV><FONT face=Arial size=2>that are not always needed.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Additional remark: In the absence of other
documentation</FONT></DIV>
<DIV><FONT face=Arial size=2>a set of specialized instance creation method helps
you to</FONT></DIV>
<DIV><FONT face=Arial size=2>understand how you should use a class. At times
this can</FONT></DIV>
<DIV><FONT face=Arial size=2>be very helpful.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Second additional remark:</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2> myClass new</FONT></DIV>
<DIV><FONT face=Arial size=2> initVariable1:
<anExpression1>;</FONT></DIV>
<DIV><FONT face=Arial size=2> initVariable2:
<anExpression2>;</FONT></DIV>
<DIV><FONT face=Arial size=2> initVariable3:
<anExpression3>.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>is of course possible, but it does not </FONT><FONT
face=Arial size=2>surpass the</FONT></DIV>
<DIV><FONT face=Arial size=2>quality of code that is generated </FONT><FONT
face=Arial size=2>by simple tools.</FONT></DIV>
<DIV><FONT face=Arial size=2>As we are not code generators we should
perhaps</FONT></DIV>
<DIV><FONT face=Arial size=2>try to do better. :-)</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Greetings,</FONT></DIV>
<DIV><FONT face=Arial size=2>Boris</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
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