Get variables list

Question

Question

Nikita Savchenko · Jun 14, 2016

Hello!

In Caché there is a way to print all current variables using write command without arguments:

USER>set Einstein = 1879
USER>set Mozart = 1756
USER>write
Einstein=1879
Mozart=1756

But is there a way to get a list of this variables? I am looking for something that would return value like $LB("Einstein", "Mozart") for this case.

Thanks!

Discussion (16)0

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Michael Braam · Jun 14, 2016

Something like this should do it:

set x=""

set x = $o(@x)

while x'="" {

write !,x," ",@x

set x = $o(@x)

}

3 0

Timothy Leavitt · Jun 14, 2016

You could always use process private globals instead of local variable names if you want to avoid collisions in local variable names.

ClassMethod GetVariables() As %List
{
    Set ^||VariableNameList = ""
    Set ^||VariableName = ""
    Set ^||VariableName = $Order(@^||VariableName)
    While (^||VariableName '= "") {
        Set ^||VariableNameList = ^||VariableNameList_$ListBuild(^||VariableName)
        Set ^||VariableName = $Order(@^||VariableName)
    }
    Quit ^||VariableNameList
}

This might do some things you don't expect depending on variable scope, though - possibly relevant depending on the use case you have in mind.

Class Demo.Variables
{

ClassMethod OuterMethod()
{
    Set x = 5
    Do ..InnerMethod()
}

ClassMethod InnerMethod() [ PublicList = y ]
{
    Set y = 10
    Write $ListToString(..GetVariables())
}

ClassMethod NoPublicListMethod()
{
    Set y = 10
    Write $ListToString(..GetVariables())
}

ClassMethod GetVariables() As %List
{
    Set ^||VariableNameList = ""
    Set ^||VariableName = ""
    Set ^||VariableName = $Order(@^||VariableName)
    While (^||VariableName '= "") {
        Set ^||VariableNameList = ^||VariableNameList_$ListBuild(^||VariableName)
        Set ^||VariableName = $Order(@^||VariableName)
    }
    Quit ^||VariableNameList
}

}

Results:

SAMPLES>kill  set z = 0 d ##class(Demo.Variables).OuterMethod()
y,z
SAMPLES>kill  set z = 0 d ##class(Demo.Variables).NoPublicListMethod()
z

1 0

score 0 · Answer 1 · 2016-06-14T08:48:39-04:00

This is awesome. It works! Wondering how many things COS has.

But it also outputs variable x. I wrapped your code into the method, and that's what I got:

ClassMethod GetVariables() As %List
{
  set UndefinedSpecialList = $LB()
  set UndefinedSpecialInt = 0
  set Undefined = ""
  set Undefined = $ORDER(@Undefined)
  while (Undefined '= "") {
    quit:($ORDER(@Undefined) = "UndefinedSpecialList")
    set $LIST(UndefinedSpecialList, $INCREMENT(UndefinedSpecialInt)) = Undefined
    set Undefined = $ORDER(@Undefined)
  }
  return UndefinedSpecialList
}

It works awesome until user specify variables named UndefinedSpecialList, UndefinedSpecialInt and Undefined. I suppose user won't ever name variables this way, of course, but the method which will consider this is the winner.

score 0 · Answer 2 · 2016-06-14T09:01:47-04:00

Thank you, Timothy! This is good, but what if user specify ^||VariableNameList process-private variable before calling the method? The value will be lost:

USER>set ^||VariableNameList = "TempVal" zwrite ##class(Test.Class).GetVariablesByTimothy()
$lb("Einstein","Mozart")
USER>write ^||VariableNameList
...TempVal is now gone!...

Maybe there is no absolutely save method to get the variables list without touching/rewriting other variables or globals. I hope it is enough just to name temporary variables as no one suggests to name.

score 0 · Answer 3 · 2016-06-14T09:34:00-04:00

Check if variable is defined beforehand and generate/use a new variable name if required:

ClassMethod GetNewVarName() As %String
{
    Set Name = "Temp"
    While $Data(@Name) {
        Set Name = Name _ $Random(100)
    }
    Return Name
}

score 0 · Answer 4 · 2016-06-14T10:23:43-04:00

OK :) But how to use this variable name generator? :)

 set myNewVarName = ..GetNewVarName() // oops, no
 set @..GetNewVarName() = "" // now it's OK, but I need to call this function once more
 set @..GetNewVarName() = $ORDER(@@..GetNewVarName()) // oops, another variable names

Things get complicated here. I think we can stop on the solutions Michael and Timothy proposed.

Thanks!

score 1 · Answer 5 · 2016-06-14T12:00:55-04:00

Here's a sneaky way to use a NEWable and SETtable system variable to cache your "safe" variable name in:

 new $etrap
 set $etrap=";"_..GetNewVarName() ; semicolon prefix makes the $ETRAP into a valid line of code (i.e. a comment)
 set @$extract($etrap,2,*)=""
 set @$extract($etrap,2,*)=$order(@@$extract($etrap,2,*))

You need more than one "safe" variable? Use subscripts of the one you've grabbed:

 set @$extract($etrap,2,*)@(1)="Some more info I need to store"

score 0 · Answer 6 · 2016-06-14T12:09:45-04:00

Nikita Savchenko · Jun 14, 2016

Tricky. Good to know, thanks!

0 0

score 0 · Answer 7 · 2016-06-14T12:03:45-04:00

As well as the suggestion of using a process-private global, Tim flags up an important point here. The $ORDER technique only enumerates public local variables.

score 1 · Answer 8 · 2016-06-15T10:24:22-04:00

a quick on-liner I use for debugging some times sends variabls to a global so that I can examine later:

s xtest="" f i=1:1 s xtest=$o(@xtest) q:xtest="" s ^ZZZZZ(xtest)=@xtest

score 0 · Answer 9 · 2016-06-15T10:50:12-04:00

Nice! Will wonder if you have some sort of more-liner, which also saves and restores objects (orefs). But I believe it is not too useful.

score 2 · Answer 10 · 2016-06-15T20:42:51-04:00

Hi,

After read all I didn't get exactly what you need. However, you can get all variables using ˆSPOOL.

If you run the following command, which uses the device 2 (ˆSPOOL) you will get all variables on the global ˆSPOOL

http://docs.intersystems.com/latest/csp/docbook/DocBook.UI.Page.cls?KEY=...

/* Writing to the ^SPOOL global */  
OPEN 2   
USE 2   
WRITE 
CLOSE 2  

/* Displaying the ^SPOOL global */  
ZW ^SPOOL

score 1 · Answer 11 · 2016-06-16T05:55:18-04:00

Timur Safin · Jun 16, 2016

Old school!

P.S.

Almost entirely forgotten about spool device

1 0

score 0 · Answer 12 · 2016-06-30T14:47:33-04:00

Thanks, Fabio!

Good to know about SPOOL device. Thank you! However, this method touches ^SPOOL global. Being set before the call, ^SPOOL global changes it's value, which is not secure for my needs.

P.S. Recently, Stuart gave me a complete answer. Thanks for your help!

score 1 · Answer 13 · 2016-06-30T13:37:03-04:00

If you are really sensitive as to not defining new local variables, and having them pollute your variable list, use the variable named % (yes, just a percent sign is a valid variable name, and happens to sort first. Here is the simple case:

    WRITE:$DATA(%) !,"%"
    NEW % SET %="%" FOR SET %=$ORDER(@%) QUIT:%="" WRITE !,%

Putting that into a routine requires one more temporary variable. %0 sorts next, then %00, %000, and so on.

VARLIST() ; SRS 2016-06-30, Returns list of local variables.
    IF $DATA(%) ; This places the existence of variable % into $TEST.
    NEW % SET %=$SELECT($TEST:$LISTBUILD("%"),1:"")
    SET:$DATA(%0) %=%_$LISTBUILD("%0")
    NEW %0 SET %0="%0"
    FOR SET %0=$ORDER(@%0) QUIT:%0="" SET %=%_$LISTBUILD(%0)
    QUIT %

Many programmers consider it acceptable, if not desirable, to use variables %, and % followed by any digits for introspection only, and therefore not worry about if % and %digits are predefined, Using %, %1, %2, %3, etc, and starting loops with SET %="%9" or something like that.

score 0 · Answer 14 · 2016-06-30T14:36:37-04:00

Thank you, Stuart!

I think this is a complete solution. I wrapped it to a class method and it works just as expected:

ClassMethod VarList() As %String
{
    IF $DATA(%) ; This places the existence of variable % into $TEST.
    NEW % SET %=$SELECT($TEST:$LISTBUILD("%"),1:"")
    SET:$DATA(%0) %=%_$LISTBUILD("%0")
    NEW %0 SET %0="%0"
    FOR {
        SET %0=$ORDER(@%0)
        QUIT:%0=""
        SET %=%_$LISTBUILD(%0)
    }
    QUIT %
}

Results with

USER > write
%=11
a=<OBJECT REFERENCE>[1@DevProject.Robot]
i=5
USER > zw ##class(DevProject.Robot).VarList()
$lb("%","a","i")
USER > kill %
USER > zw ##class(DevProject.Robot).VarList()
$lb("a","i")