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<div class=Section1>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>I am a new user of the component system (currently using it
with Twisted, not using <span class=SpellE>zope</span> itself). I’m not
sure I understand all the philosophy behind its design. Nevertheless, I believe
the following behavior is not the best:<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>>>> a = <span class=SpellE><span class=GramE>Int</span></span><span
class=GramE>(</span> <span class=SpellE>missing_value</span> = -1 )<o:p></o:p></span></font></p>
<p class=MsoNormal><span class=SpellE><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'>Traceback</span></font></span><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'> (most
recent call last):<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span style='mso-spacerun:yes'> </span>File "<<span
class=SpellE>stdin</span>>", line 1, <span class=GramE>in ?</span><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span style='mso-spacerun:yes'> </span>File "c:\python24\lib\site-packages\zope\schema\_bootstrapfields.py",
line 351, in __init__<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span style='mso-spacerun:yes'> </span><span
class=GramE>super(</span><span class=SpellE>Int</span>, self).__init__(*<span
class=SpellE>args</span>, **<span class=SpellE>kw</span>)<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span style='mso-spacerun:yes'> </span>File "c:\python24\lib\site-packages\zope\schema\_bootstrapfields.py",
line 231, in __init__<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span style='mso-spacerun:yes'> </span><span
class=SpellE>self.min</span> = min<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span style='mso-spacerun:yes'> </span>File "c:\python24\lib\site-packages\zope\schema\_bootstrapfields.py",
line 42, in __set__<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span style='mso-spacerun:yes'> </span><span
class=SpellE><span class=GramE>inst.validate</span></span><span class=GramE>(</span>value)<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span style='mso-spacerun:yes'> </span>File "c:\python24\lib\site-packages\zope\schema\_bootstrapfields.py",
line 138, in validate<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span style='mso-spacerun:yes'> </span><span
class=SpellE>self._<span class=GramE>validate</span></span><span class=GramE>(</span>value)<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span style='mso-spacerun:yes'> </span>File "c:\python24\lib\site-packages\zope\schema\_bootstrapfields.py",
line 240, in _validate<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span style='mso-spacerun:yes'> </span><span
class=GramE>super(</span>Orderable, self)._validate(value)<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span style='mso-spacerun:yes'> </span>File "c:\python24\lib\site-packages\zope\schema\_bootstrapfields.py",
line 165, in _validate<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span style='mso-spacerun:yes'> </span><span
class=GramE>raise</span> <span class=SpellE>WrongType</span>(value, <span
class=SpellE>self._type</span>)<o:p></o:p></span></font></p>
<p class=MsoNormal><span class=SpellE><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'>zope.schema._bootstrapinterfaces.WrongType</span></font></span><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>: (None, (<type
'<span class=SpellE>int</span>'>, <type 'long'>))<o:p></o:p></span></font></p>
<div style='border:none;border-bottom:solid windowtext 1.0pt;mso-border-bottom-alt:
solid windowtext .75pt;padding:0in 0in 1.0pt 0in'>
<p class=MsoNormal style='border:none;mso-border-bottom-alt:solid windowtext .75pt;
padding:0in;mso-padding-alt:0in 0in 1.0pt 0in'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
</div>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>What is happening is that “min” (and max) <span
class=GramE>are</span> <span class=SpellE>ValidatedProperties</span> of Orderable.
When a “<span class=SpellE>missing_value</span>” is supplied, min =
<span class=GramE>None</span> (by default) is checked and fails validation.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>One solution is to change “None” into <span
class=SpellE>missing_value</span> in the Orderable __init__. More exhaustively,
min, max, and default should have defaults as “__<span class=SpellE>missing_value_marker</span>”
in the Orderable __init__ (using the trick in <span class=SpellE>Field.__init</span>__),
which would then be converted to the actual <span class=SpellE>missing_value</span>,
if specified, or <span class=GramE>None</span>, if not.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>This gives me the following __init__ in <span class=SpellE>zope.schema_bootstrapfields.Orderable</span>:<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span style='mso-spacerun:yes'> </span>__<span
class=SpellE>missing_value_marker</span> = <span class=GramE>object()</span><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span style='mso-spacerun:yes'> </span><span
class=GramE>def</span> __init__(self, min=__<span class=SpellE>missing_value_marker</span>,
max=__<span class=SpellE>missing_value_marker</span>,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span
style='mso-spacerun:yes'>
</span><span class=GramE>default</span>=__<span class=SpellE>missing_value_marker</span>,
**<span class=SpellE>kw</span>):<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span
style='mso-spacerun:yes'> </span>#
Set min and max to <span class=GramE>None</span> so that we can validate if<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span
style='mso-spacerun:yes'> </span># <span
class=GramE>one</span> of the super methods invoke validation.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span
style='mso-spacerun:yes'> </span><span
class=SpellE>self.min</span> = <span class=GramE>None</span><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span
style='mso-spacerun:yes'> </span><span
class=SpellE>self.max</span> = <span class=GramE>None</span><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span
style='mso-spacerun:yes'> </span><span
class=GramE>super(</span>Orderable, self).__init__(**<span class=SpellE>kw</span>)<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span
style='mso-spacerun:yes'> </span>#
make sure that unspecified min, max, default get correct missing value<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span
style='mso-spacerun:yes'> </span><span
class=GramE>try</span>: missing = <span class=SpellE>self.missing_value</span><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span
style='mso-spacerun:yes'> </span><span
class=GramE>except</span> <span class=SpellE>AttributeError</span>: missing = None<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span
style='mso-spacerun:yes'>
</span><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span
style='mso-spacerun:yes'> </span><span
class=GramE>if</span> min is <span class=SpellE>self.__missing_value_marker</span>:
min = missing<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span
style='mso-spacerun:yes'> </span><span
class=GramE>if</span> max is <span class=SpellE>self.__missing_value_marker</span>:
max = missing<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span
style='mso-spacerun:yes'> </span><span
class=GramE>if</span> default is <span class=SpellE>self.__missing_value_marker</span>:
default = missing<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span style='mso-spacerun:yes'> </span><span
style='mso-spacerun:yes'> </span># <span
class=GramE>Now</span> really set min and max<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span
style='mso-spacerun:yes'> </span><span
class=SpellE>self.min</span> = min<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span
style='mso-spacerun:yes'> </span><span
class=SpellE>self.max</span> = max<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span
style='mso-spacerun:yes'> </span># <span
class=GramE>We've</span> taken over setting default so it can be limited by min<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span
style='mso-spacerun:yes'> </span># <span
class=GramE>and</span> max.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span
style='mso-spacerun:yes'> </span><span
class=SpellE>self.default</span> = default<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>(But I don’t know if constraints should (always?)
apply to each other. For instance, if “min” were actually defined
as the largest value smaller than the range, it wouldn’t validate against
itself.)<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>- Shaun<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
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