Field exists on a view

[Amferreira]

How can check (programmatically) if a field exist on a view ?

 

[Nigel Gomm]

FSIZE() will tell you the size of the column (or zero if not there).... but because of the DBASE history you need to have SET COMPATIBLE OFF first

so

SET COMPATIBLE OFF
IF FSIZE('mycolumn','myalias') > 0

or another way is to check

if !EMPTY(FIELD('mycolumn','myalias'))

in both cases if you omit the alias it defaults to the currently selected workarea.

hth

n

 

[mjcmkrsr]

Hi,

You may want to have a look at the AFIELDS() function

hth

MarK

 

[Mike Lewis]

I'd vote against FSIZE(). HackFox explains the reason better than I could:

FSIZE() is a horror show ... it's one of the few [functions] that is affected by the dreaded SET COMPATIBLE command ... Our advice: leave COMPATIBLE SMART (FoxPlus) and use ADIR() to get file sizes

.

... or, in this case, use AFIELDS() to get field sizes.

So you would use AFIELDS() to get all the field names from the view into an array. Then ASCAN() the array to see if the one you are interested in is present.

Mike





__________________________________
Mike Lewis (Edinburgh, Scotland)

Visual FoxPro articles, tips and downloads

 

[mjcmkrsr]

Hi,

or use the FCOUNT() and FIELD() functions

LOCAL lnFields

use lvMyView

lnFields = FCOUNT("lvMyView")

FOR i = 1 to lnFields
[indent]? FIELD(i, "lvMyView") [/indent]
ENDFOR

CLOSE ALL

hh

MarK

 

[Mike Lewis]

Or how about using TYPE():

[tt]
? TYPE("MyView.MyField") <> "U"[/tt]

where MyView is the name of the view, and MyField is the name of the field. (And don't forget the quotes.)

Mike

__________________________________
Mike Lewis (Edinburgh, Scotland)

Visual FoxPro articles, tips and downloads

 

[Nigel Gomm]

Mike,

fair point about set compatible.

i have it always off and don't change it ever (for fear of breaking other commands affected by it).

So FSIZE() is safe in that environment.

But FIELD() (or TYPE - hadn't thought of that) would be simpler than searching an array.

Odd in a way there's no direct command and we have to infer from other commands.

n

 

[mjcmkrsr]

Hi,

...

or if you want a printout

LIST STRUCTURE NOCONSOLE TO FILE lvStructure.txt

hth

Mark

 

[mjcmkrsr]

Hi

... would be simpler than searching an array.

hmm

LOCAL ARRAY laStructure[1]

use lvMyView

= AFIELDS(laStructure, "lvMyView")

IF ASCAN(laStructure, "MyFieldName", 1, -1, 1, 1) > 0
[indent]MyFieldName exists[/indent]
ELSE
[indent]MyFieldName does not exist[/indent]
ENDIF

CLOSE ALL

Btw, and in order to state the obvious, the two approaches differ: the combination FCOUNT() + FIELD() yields the name of the field whereas TYPE() and AFIELDS() + ASCAN() assume you know the field's name

hth

MarK