| Pointer Behavior Objects Vs Plain routines? [message #32093] |
Wed, 11 September 2002 07:54 |
savoie
Messages: 68
Registered: September 1996
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Member |
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Hey all,
O.k. I'm looking at some pointer weridness. Well, I'm calling it weirdness
because I obviously don't understand something that is happening. There are
two examples below.
The first is just two routines. test: creates a pointer, calls changePtr
with a null pointer as an argument; and changePtr: which just assigns a
string the the passedPtr. This examples shows that if you pass a pointer to
a procedure, assign something to that pointer, you can retrieve it after
exit.
The rest of the routines are a simple object with a couple of methods,
showing exactly the opposite effect. When the object's CHANGEPTR method is
called, self.myptr doesn't seem to be able to be changed on return.
So if someone here can please enlighten me, I would be very appreciative.
What's different between the object calls and the plain procedure calls?
Thanks
Matt Savoie
National Snow and Ice Data Center, Boulder, CO
p.s. Just because I haven't had to ask questions here in a while, doesn't
mean I haven't been getting them answered. Google groups for this has saved
my behind on many more than one occasion. So additional thanks for everyone
helping answer questions on this group.
;; ------------------------------------------------------------ ----------
;; These are distilled as much as I could think of to produce the behavior
;; that I don't understand. PRO CHANGEPTR, passedPtr
passedPtr = ptr_new('This is weird?')
END
PRO TEST
ptr = ptr_new()
print, ptr_valid(ptr)
changePtr, ptr
print, ptr_valid(ptr)
print, *ptr
END
;;---------------------------------------------------------- ------------
PRO WEIRD::DOIT, ptrInside
ptrInside = ptr_new('Why can not I change this?')
END
PRO WEIRD::CHANGEPTR
self -> doIt, self.myptr
END
PRO WEIRD::SHOWME
print, ptr_valid(self.myptr)
IF (ptr_valid(self.myptr)) THEN print, *self.myptr
END
FUNCTION INIT
return, 1
END
PRO WEIRD__DEFINE
objectClass = {weird, $
myptr:ptr_new() $
}
END
PRO TESTWEIRD
w = obj_new('weird')
w -> showMe
w -> ChangePtr
w -> ShowMe
END
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