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SKILL++ class slots

acook

I have a few question on slots in a class. Given the following class that implements string utilities:

defclass( String()

 ()

(

(str @initarg nil) ; The string

(len @initarg nil); The length of the string 

)

)

defmethod( Length ((s String))

s->len = strlen(str)

) 

 

Is there a way to trigger Length() whenever the slot "str" is updated? I know I could make another method like "SetStr" but that is a little messy, I also have to remember to always use that method and not set str directly.

Thank you,

Aaron 

Parents
  • Andrew Beckett

    Aaron,

    No, SKILL++ (like CLOS) doesn't work that way. The C++ like syntax might make it look as if it does, but it doesn't. It's not a flaw in the language, it's just different from C++.  You can create a writer method, using @writer, but in this case you want some specific behaviour.

    Given that when you do obj->str="whatever", it's really doing (putpropq obj "whatever" str), there's not really any difference with writing SetStr(obj "whatever"). It's not "messy" - it's just the way it's done in the language - you use procedural abstraction.

    Regards,

    Andrew.

Reply
  • Andrew Beckett

    Aaron,

    No, SKILL++ (like CLOS) doesn't work that way. The C++ like syntax might make it look as if it does, but it doesn't. It's not a flaw in the language, it's just different from C++.  You can create a writer method, using @writer, but in this case you want some specific behaviour.

    Given that when you do obj->str="whatever", it's really doing (putpropq obj "whatever" str), there's not really any difference with writing SetStr(obj "whatever"). It's not "messy" - it's just the way it's done in the language - you use procedural abstraction.

    Regards,

    Andrew.

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