Externals Under 2.7.x
lists at mangomultimedia.com
Sat Feb 10 13:24:07 EST 2007
On Feb 10, 2007, at 10:02 AM, Mark Wieder wrote:
>> As for storing your result in the "it" variable, one potential issue
>> I see (if I am understanding correctly) is that functions defined in
>> an external would have different basic behavior than functions
>> defined in Revolution (Transcript). Any function defined in an
>> external would have to be called like this in order to work properly:
>> put getTheNumberFour() into theError
>> answer it -- CONTAINS THE NUMBER "4"
>> because if the user called the external function like this:
>> get getTheNumberFour()
>> then both "it" and "the result" would contain the error message.
>> Plus you would lose the ability to put result of the function into a
>> meaning variable name without adding another assignment (i.e. put it
>> into theMeaningVariableName).
> Actually that's the way functions work. The internal db and xml
> handlers return a value to you and you have to check the result to see
> if it (trying to refer to these natural language syntax values is
> getting a bit difficult) to see if it contains "revxml err" or
> something like that.
The rev externals do return the error string as the result of the
function but they don't explicitly store any value in the "it"
variable. For example, if you do this:
on mouseUp pMouseBtnNo
put revXMLNodeContents(theNonExistentXMLTreeID,"no node") into
put it & cr & theContent
The message box would print:
xmlerr, bad document id
Whereas with your interesting trick it would be empty I believe.
So with the rev externals you end up checking the same value for
either an error string or the returned value. This is the method
like least of all for error reporting.
Blue Mango Learning Systems - www.bluemangolearning.com
trevor at bluemangolearning.com
More information about the Use-livecode