Does a Control Exist?
richmondmathewson at gmail.com
Sun Nov 24 20:55:28 CET 2013
On 24.11.2013 21:37, Ray wrote:
> Really? When I do this...
> on mouseUp
> put "test 1" into fld "Cats" -- this field does not
> put "test 2" into fld "Dogs" -- this field does exist
> end mouseUp
> the script editor window pops up on the first line alerting me with an
> error. It never progresses to the second line. I haven't tried this
> in a standalone but I'm pretty sure the script will stop all the same
> just as soon as it encounters the first line.
That WILL halt the script, hence the need to use
if exists(some control) then
If you try to pour a bucket of water into a non-existent bath-tub you
will get wet feet, at which point
you will be so cheesed-off you will be unable to proceed with whatever
you had planned to do subsequently.
> Nonetheless, I'm not all that sure I'm in favor of changing things.
> The idea just occurred to me so I decided to see what other devs on
> the list think about it as long as it's a relatively low traffic Sunday.
> On 11/24/2013 12:27 PM, Richmond wrote:
>> On 24.11.2013 18:58, Ray wrote:
>>> Yeah, I know there are various ways of checking whether the control
>>> exists or not before proceeding. I just wondered whether anybody
>>> else thought it might be nice not to have to do that since it does
>>> halt the script if the control doesn't exist.
>>>> Well, surely the trick is to do something like this:
>>>> if exists(fld "My Field") then
>>>> put fld "My Field" into myVar
>>>> end if
>> I must be missing something . . .
>> I'm not sure what you mean by "halt the script".
>> Certainly, if fld "My Field" does not exist the script won't put
>> anything into myVar, after all, it's
>> not meant to.
>> I just tried something else, in an attempt to understand what you
>> meant by "halt the script";
>> I set up a stack with one fld "cheese" and a one btn "Button"
>> containing this script:
>> on mouseUp
>> if exists(fld "dogs") then
>> put "yap" into fld "dogs"
>> end if
>> if exists(fld "cheese") then
>> put "zip" into fld "cheese"
>> end if
>> end mouseUp
>> Now, as fld "dogs" does not exist, "yap" appears nowhere, but "zip"
>> does end up in fld "cheese";
>> so the fact that fld "dogs" does not exists does not stop the rest of
>> the script from doing what it should.
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