9 Aug
2007
9 Aug
'07
2:10 p.m.
hey i working through the magritte tutorial excercises. need ome help with
exercise 18. it says "Add a class-instance variable to the MAPersonModel
called CustomDescription. initialize it with an emptyinstance of
maContainer".
i did the following to add a class-instance variable
MAPersonModel class
instanceVariableNames: 'CustomDescription'
how do i initialize this variable
if i override the initialize method on the class
i get the follwoing warning from system browser "initialize is used in the
existing class system, overriding can cause serious problem is this really
what you want to do ?"
am i doing something wrong, can some one help me ?
im not sure what the difference between class variable and class-instance
variable
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9 Aug
9 Aug
3:15 p.m.
i get the follwoing warning from system browser
"initialize is used
in the
existing class system, overriding can cause serious problem is this
really
what you want to do ?"
I don't know why Squeak is complaining here. You can safely ignore
this warning.
am i doing something wrong, can some one help me ?
No, everything correct.
im not sure what the difference between class variable
and class-
instance
variable
From the Smalltalk FAQ [1]: Class instance variables are similar to
class variables, except that they are created for eachsubclass of the
defining class. When a class declares a class instance variable, a
new variable is created for each subclass of that class. Each
subclass then has its own instance of the variable and retains its
own value for the variable, but each subclass has a variable with the
same name. Only class methods of a class and its subclasses can refer
to class instance variables; instance methods cannot.
Cheers,
Lukas
[1] http://www.faqs.org/faqs/smalltalk-faq/
--
Lukas Renggli
http://www.lukas-renggli.ch
6:56 p.m.
cool thanks lukas
exercise 18 also ays "Override #description on the instance-side, call super
and
compose it with the CustomDescription." what does this mean how do i compose
it
Lukas Renggli-2 wrote:
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i get the follwoing warning from system browser
"initialize is used
in the
existing class system, overriding can cause serious problem is this
really
what you want to do ?"
I don't know why Squeak is complaining here. You can safely ignore
this warning.
am i doing something wrong, can some one help me
?
No, everything correct.
im not sure what the difference between class
variable and class-
instance
variable
From the Smalltalk FAQ [1]: Class instance variables are similar to
class variables, except that they are created for eachsubclass of the
defining class. When a class declares a class instance variable, a
new variable is created for each subclass of that class. Each
subclass then has its own instance of the variable and retains its
own value for the variable, but each subclass has a variable with the
same name. Only class methods of a class and its subclasses can refer
to class instance variables; instance methods cannot.
Cheers,
Lukas
[1] http://www.faqs.org/faqs/smalltalk-faq/
--
Lukas Renggli
http://www.lukas-renggli.ch
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8:53 p.m.
2007/8/9, isaiah <cappadonza(a)hotmail.com>om>:
cool thanks lukas
exercise 18 also ays "Override #description on the instance-side, call super
and
compose it with the CustomDescription." what does this mean how do i compose
it
I guess it means something like:
MyObject>>description
^ super description copy
add: self customDescription;
yourself
I'm not sure, but I think #copy is important after the call to super.
--
Damien Cassou
8:59 p.m.
From the Smalltalk FAQ [1]: Class instance variables
are
similar to class variables, except that they are created for
eachsubclass of the defining class. When a class declares a
class instance variable, a new variable is created for each
subclass of that class. Each subclass then has its own
instance of the variable and retains its own value for the
variable, but each subclass has a variable with the same
name. Only class methods of a class and its subclasses can
refer to class instance variables; instance methods cannot.
Cheers,
Lukas
Or to put it simply, classes are objects too, and all objects have instance
variables.
Ramon Leon
http://onsmalltalk.com
6349
days inactive
6349
days old
4 comments
4 participants
participants (4)
-
Damien Cassou -
isaiah -
Lukas Renggli -
Ramon Leon