| how to get info on object fields [message #9782] |
Mon, 25 August 1997 00:00  |
Mirko Vukovic
Messages: 124
Registered: January 1996
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Senior Member |
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Hi,
I was trying to write a general extraction routine for objects. The
idea was to pass the name of a field, it would check if the field
exists, get its tag number and extract it. It would work on the object
as if it were a structure. But TAG_NAMES does not work on objects
(which does make sense as SELF is still an object (type =11), not a
structure). (see code below for my implementation).
I like using objects, but sometimes they are too cumbersome for
debugging purposes. I would also like to have a set of general routines
applicable to all objects (via inheritance). That is why a general
routine for extracting a field would be nice. Any clues how I might go
about it?
FUNCTION structured::extract,arg,depointer = depointer
; check if arg is a valid field name
ii = where(tag_names(self) EQ strupcase(arg),count)
IF count NE 0 THEN begin
type = size(self.(ii))
type = type[type[0]+1]
IF keyword_set(depointer) THEN if type EQ 10 THEN
return,*self.(ii)
return,self.(ii)
ENDIF ELSE BEGIN
message,/info,'Invalid field name provided'
print,'You specified'+arg
print,'Available fields are:'
print,tag_names(self)
return,0
ENDELSE
--
Mirko Vukovic, Ph.D 3075 Hansen Way M/S K-109
Novellus Systems Palo Alto, CA, 94304
415/424-4969 mirko.vukovic@varian.grc.com
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| Re: how to get info on object fields [message #9869 is a reply to message #9782] |
Thu, 28 August 1997 00:00  |
J.D. Smith
Messages: 214
Registered: August 1996
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Senior Member |
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David Fanning wrote:
>
> Mirko Vukovic writes:
>
>> I was trying to write a general extraction routine for objects. The
>> idea was to pass the name of a field, it would check if the field
>> exists, get its tag number and extract it. It would work on the object
>> as if it were a structure. But TAG_NAMES does not work on objects
>> (which does make sense as SELF is still an object (type =11), not a
>> structure). (see code below for my implementation).
>>
>> I like using objects, but sometimes they are too cumbersome for
>> debugging purposes. I would also like to have a set of general routines
>> applicable to all objects (via inheritance). That is why a general
>> routine for extracting a field would be nice. Any clues how I might go
>> about it?
>
> I used this code to get something working in just a few minutes.
> These objects can have superclasses, of course, and I am not
> checking for that. You could use Obj_Class to find all the
> superclass structures in an iterative way. The code would not
> be too hard to implement.
>
> The way this code works is to use Obj_Class to get the
> name of the object, which is the name of the structure
> you want. I create the right kind of structure with
> the Execute command. To extract the field, I have to
> use a second Execute statement.
>
> FUNCTION OBJECT::EXTRACT, field
>
> ; Check if FIELD is a valid field name. If it is,
> ; return the field. If not, return -1.
>
> thisClass = Obj_Class(self)
> ok = Execute('thisStruct = {' + thisClass + '}')
> structFields = Tag_Names(thisStruct)
> index = WHERE(structFields EQ StrUpCase(field), count)
> IF count EQ 1 THEN BEGIN
> ok = Execute('Return, SELF.' + structFields(index(0)))
> ENDIF ELSE BEGIN
> Message, 'Can not find field "' + field + $
> '" in structure.', /Informational
> RETURN, -1
> ENDELSE
> END
>
> This should give you some ideas.
>
> Cheers,
>
Looks good. I have one improvement, though. You can save yourself the
second execute by using the handy field index trick, just like for
structures.. i.e. just write:
return, SELF.(index[0])
Also, you needn't have the superclass info search, since the INHERITS
definition in a class struct define simply includes all fields there.
JD
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| Re: how to get info on object fields [message #9881 is a reply to message #9782] |
Mon, 25 August 1997 00:00 |
davidf
Messages: 2866
Registered: September 1996
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Senior Member |
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Mirko Vukovic writes:
> I was trying to write a general extraction routine for objects. The
> idea was to pass the name of a field, it would check if the field
> exists, get its tag number and extract it. It would work on the object
> as if it were a structure. But TAG_NAMES does not work on objects
> (which does make sense as SELF is still an object (type =11), not a
> structure). (see code below for my implementation).
>
> I like using objects, but sometimes they are too cumbersome for
> debugging purposes. I would also like to have a set of general routines
> applicable to all objects (via inheritance). That is why a general
> routine for extracting a field would be nice. Any clues how I might go
> about it?
I used this code to get something working in just a few minutes.
These objects can have superclasses, of course, and I am not
checking for that. You could use Obj_Class to find all the
superclass structures in an iterative way. The code would not
be too hard to implement.
The way this code works is to use Obj_Class to get the
name of the object, which is the name of the structure
you want. I create the right kind of structure with
the Execute command. To extract the field, I have to
use a second Execute statement.
FUNCTION OBJECT::EXTRACT, field
; Check if FIELD is a valid field name. If it is,
; return the field. If not, return -1.
thisClass = Obj_Class(self)
ok = Execute('thisStruct = {' + thisClass + '}')
structFields = Tag_Names(thisStruct)
index = WHERE(structFields EQ StrUpCase(field), count)
IF count EQ 1 THEN BEGIN
ok = Execute('Return, SELF.' + structFields(index(0)))
ENDIF ELSE BEGIN
Message, 'Can not find field "' + field + $
'" in structure.', /Informational
RETURN, -1
ENDELSE
END
This should give you some ideas.
Cheers,
David
-----------------------------------------------------
David Fanning, Ph.D.
Fanning Software Consulting
Customizable IDL Programming Courses
Phone: 970-221-0438 E-Mail: davidf@dfanning.com
Coyote's Guide to IDL Programming: http://www.dfanning.com
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