Hi ! Actually it is probably a very simple Squeak concept which I haven't understood, yet.
Serving as an simple example, I would like to write a method, which accepts a Class as argument and which return the Superclass of that Class. The problem is that the argument must be an instance of String, that means the argument aClassName contains an actual class name (e.g. aClassName = 'Object'. or aClassName = 'ClassBuilder'), however, this is just a String object.
returnSuperClass: aClassName |aSuperClass|
aSuperClass := aClassName superclass.
^ aSuperClass.
Obviously this method won't work, because aClassName is just an instance of ByteString. And instances of ByteString cannot understand the message superclass.
So I need the actual class object which the content of the String aClassName represents. How can I achieve ? Or how can I make this method correct ? (it is imperative, that the argument aClassName is a String).
Thanks for you help in advance.
Best Regards Warakorn
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Hello Warakorn,
try: Smalltalk at: #MonthMorph inspect
Cheers
Herbert mailto:herbertkoenig@gmx.net WP> Hi ! WP> Actually it is probably a very simple Squeak concept which I haven't understood, yet.
WP> Serving as an simple example, I would like to write a method, WP> which accepts a Class as argument and which return the Superclass WP> of that Class. WP> The problem is that the argument must be an instance of WP> String, that means the argument aClassName contains an actual WP> class name (e.g. aClassName = 'Object'. or aClassName = WP> 'ClassBuilder'), however, this is just a String object.
WP> returnSuperClass: aClassName WP> |aSuperClass|
WP> aSuperClass := aClassName superclass.
WP> ^ aSuperClass.
WP> Obviously this method won't work, because aClassName is just WP> an instance of ByteString. And instances of ByteString cannot WP> understand the message superclass.
WP> So I need the actual class object which the content of the String aClassName represents. WP> How can I achieve ? Or how can I make this method correct ? WP> (it is imperative, that the argument aClassName is a String).
WP> Thanks for you help in advance.
WP> Best Regards WP> Warakorn
WP> Have a burning question? Go to Yahoo! Answers and get answers from real people who know.
Hello Warakorn,
HK> try: HK> Smalltalk at: #MonthMorph inspect
I got some more time, so here is a longer Version:
Smalltalk is a Dictionary which afaik contains the names of all global symbols. So if you got a String, send it asSymbol and then look it up in that Dictionary.
Actually Smalltalk is a SystemDictionary, if you are interested in exploring. The class comment has an example.
Before writing or removing entries in this Dictionary, make sure you know what you're doing :-))
So your code should be something like:
returnSuperClass: aClassName |aSuperClass aClass|
aClass := Smalltalk at: aClassName asSymbol. aSuperClass := aClass superclass.
^ aSuperClass.
Cheers
Herbert
A better alternative would be
Smalltalk classNamed: 'Object'
avoiding the "low level" #at: and #asSymbol protocol. Does some more checks, too.
- Bert -
On Jan 16, 2007, at 14:33 , Herbert König wrote:
Hello Warakorn,
HK> try: HK> Smalltalk at: #MonthMorph inspect
I got some more time, so here is a longer Version:
Smalltalk is a Dictionary which afaik contains the names of all global symbols. So if you got a String, send it asSymbol and then look it up in that Dictionary.
Actually Smalltalk is a SystemDictionary, if you are interested in exploring. The class comment has an example.
Before writing or removing entries in this Dictionary, make sure you know what you're doing :-))
So your code should be something like:
returnSuperClass: aClassName |aSuperClass aClass|
aClass := Smalltalk at: aClassName asSymbol. aSuperClass := aClass superclass.
^ aSuperClass.
Cheers
Herbert
Beginners mailing list Beginners@lists.squeakfoundation.org http://lists.squeakfoundation.org/mailman/listinfo/beginners
This doesn't work either, because again (Smalltalk at: aClassName) is returning just a ByteString but not (e.g.) Object class or (e.g.) ClassBuilder class .
Lets assume in the calling method is written: returnSuperClass: '#Object'. Note: the Argument must be an instance of String.
returnSuperClass: aClassName |aSuperClass|
aSuperClass := (Smalltalk at: aClassName) superclass.
^ aSuperClass.
Nope, this does'nt work.
Herbert König herbertkoenig@gmx.net wrote: Hello Warakorn,
try: Smalltalk at: #MonthMorph inspect
Cheers
Herbert mailto:herbertkoenig@gmx.net WP> Hi ! WP> Actually it is probably a very simple Squeak concept which I haven't understood, yet.
WP> Serving as an simple example, I would like to write a method, WP> which accepts a Class as argument and which return the Superclass WP> of that Class. WP> The problem is that the argument must be an instance of WP> String, that means the argument aClassName contains an actual WP> class name (e.g. aClassName = 'Object'. or aClassName = WP> 'ClassBuilder'), however, this is just a String object.
WP> returnSuperClass: aClassName WP> |aSuperClass|
WP> aSuperClass := aClassName superclass.
WP> ^ aSuperClass.
WP> Obviously this method won't work, because aClassName is just WP> an instance of ByteString. And instances of ByteString cannot WP> understand the message superclass.
WP> So I need the actual class object which the content of the String aClassName represents. WP> How can I achieve ? Or how can I make this method correct ? WP> (it is imperative, that the argument aClassName is a String).
WP> Thanks for you help in advance.
WP> Best Regards WP> Warakorn
WP> Have a burning question? Go to Yahoo! Answers and get answers from real people who know.
_______________________________________________ Beginners mailing list Beginners@lists.squeakfoundation.org http://lists.squeakfoundation.org/mailman/listinfo/beginners
--------------------------------- Don't get soaked. Take a quick peak at the forecast with theYahoo! Search weather shortcut.
What makes you think it does not return a class object? It does.
But note that you have to use a symbol (#Object) not a String ('Object') when you use #at:. Of course. '#Object' does not make any sense. If you use #classNamed:, both a String and a Symbol will work.
- Bert -
On Jan 16, 2007, at 14:41 , Warakorn Paphrawat wrote:
This doesn't work either, because again (Smalltalk at: aClassName) is returning just a ByteString but not (e.g.) Object class or (e.g.) ClassBuilder class .
Lets assume in the calling method is written: returnSuperClass: '#Object'. Note: the Argument must be an instance of String.
returnSuperClass: aClassName |aSuperClass|
aSuperClass := (Smalltalk at: aClassName) superclass.
^ aSuperClass.
Nope, this does'nt work.
Herbert König herbertkoenig@gmx.net wrote: Hello Warakorn,
try: Smalltalk at: #MonthMorph inspect
Cheers
Herbert mailto:herbertkoenig@gmx.net WP> Hi ! WP> Actually it is probably a very simple Squeak concept which I haven't understood, yet.
WP> Serving as an simple example, I would like to write a method, WP> which accepts a Class as argument and which return the Superclass WP> of that Class. WP> The problem is that the argument must be an instance of WP> String, that means the argument aClassName contains an actual WP> class name (e.g. aClassName = 'Object'. or aClassName = WP> 'ClassBuilder'), however, this is just a String object.
WP> returnSuperClass: aClassName WP> |aSuperClass|
WP> aSuperClass := aClassName superclass.
WP> ^ aSuperClass.
WP> Obviously this method won't work, because aClassName is just WP> an instance of ByteString. And instances of ByteString cannot WP> understand the message superclass.
WP> So I need the actual class object which the content of the String aClassName represents. WP> How can I achieve ? Or how can I make this method correct ? WP> (it is imperative, that the argument aClassName is a String).
WP> Thanks for you help in advance.
WP> Best Regards WP> Warakorn
WP> Have a burning question? Go to Yahoo! Answers and get answers from real people who know.
Beginners mailing list Beginners@lists.squeakfoundation.org http://lists.squeakfoundation.org/mailman/listinfo/beginners
Don't get soaked. Take a quick peak at the forecast with theYahoo! Search weather shortcut. _______________________________________________ Beginners mailing list Beginners@lists.squeakfoundation.org http://lists.squeakfoundation.org/mailman/listinfo/beginners
Hello Warakorn,
WP> This doesn't work either, because again (Smalltalk at: WP> aClassName) is returning just a ByteString but not (e.g.) WP> Object class or (e.g.) ClassBuilder class .
Copied from a Workspace:
(Smalltalk at: 'MonthMorph' asSymbol) superclass inspect
This returns an inspector with AlignmentMorph class.
I guess you omitted asSymbol and my string doesn't contain the hash sign.
Please also regard Bert's post he's the professional, I'm still the beginner.
Cheers
Herbert mailto:herbertkoenig@gmx.net
The method Object>>#class does what you want. Since it is defined on Object you can send the message to any object, including a string.
returnSuperClass: aClassName |aSuperClass|
aSuperClass := aClassName class superclass.
^ aSuperClass.
The above method body could be a one liner: ^aClassName class superclass
Doh! Sorry, didn't read carefully (or the whole thread).
Bert is right: Smalltalk classNamed: 'Object'
On 1/16/07, David Mitchell david.mitchell@gmail.com wrote:
The method Object>>#class does what you want. Since it is defined on Object you can send the message to any object, including a string.
returnSuperClass: aClassName |aSuperClass|
aSuperClass := (Smalltalk classNamed: aClassName) superclass.
^ aSuperClass.
And now the one liner: ^(Smalltalk classNamed: aClassName) superclass.
beginners@lists.squeakfoundation.org
-
Bert Freudenberg -
David Mitchell -
Herbert König -
Warakorn Paphrawat